complete unix commands

4

UNIX COMMANDS1. $ LOGNAME

: It displays the current user information

2. $PWD

: present working directory

3. $DATE

: It displays the system date & time

4. $clear

: To clear the screen

5. $cal

: it current month and year

6. $cal 2000

: Displays the 2000 year calendar

7. $cal 8 2006

: displays the 8th month of 2006

8. $exit or logout

: exit from current user account

9. $ who

: displays the all user in who are currently working on server

10. $finger

: displays the all user who are currently working on server with more information11. Who am I

: displays current user information12. Which or where : displays the location of the given commandMy Commands:

Du sk filename : to find the size of one file Du sk test.txtDu sk filename1 filename2 . : to find size of multiple files

Du sk test.txt test2.txt

Du a Directory name : Give the size of all files in that directory.

Du sk * also can be used to find size of all the files.

Du a In Bound : It List size of all files/Folder size in present directoryDu -[akhrstx]: Du for folder can be used with any of these charactersBut I am getting same result for Du [trx]

Du h In Bound : consider size of directory while calcualatingE:\files in ds>du -h

512B ./In Bound/testing_UNIX

14.50KB ./In Bound

153.50KB ./Out Bound

327.00KB .How to find all the files in all the directories in that folder?Suppose Files in Ds is the folder which has so many files and also 2 Folders In Bound and Out Bound. We want the files present in In Bound and also Out bound, In that case what needs to be used?Ls R

Syn: $which pwd

13. Cat

: is use to create new files or to open exiting files or to append data to the exiting files

Create: cat >filename

-----------

-----------cntl+d

Redirect: cat file1 file2 file3 >file4--------(redirect outputAppend: cat >>filename--------( single file $cat file1 file2 file3 >>EMP------(multi files-----------

-----------cntl+d

Open file: cat .filename---------for hidden files

14. Touch

: It is used to create an empty file i.e. 0 byte fileSYN: $ touch filename

$ touch file1 file2 file3---------( create multiple files

15. rm

: deleting files or directories

EX

rm filename----------------(deleting single file

rm -i filename--------------(deleting files with confirmation

rm file1 file2----------------(deleting multiple files

rmdir dirname--------------(deleting the directory but the directory must be empty

rm -r dirname-------------(deleting directory recursively (i.e. with tree str)xrm ri dirname-------------(remove directory with confirmation

rm * ---------------------( it delets all files

rm -I *--------------------(delets all files with confirmationrm t* ---------------------(it delets whose file name starts with tHow to delete the directory which is not empty?Ex: Rm r Testing_Unix.16. mkdir

: creating directories

Syn: $mkdir dirnameSys: $Mkdir .dirname------------(hidden directory17. Cd

: change directorySys: $cd abc

$pwd------/home/madhav/abc using above cmd we can come out from abc now we at //home/madhav

cd..---------------------------(to come out from current directory

cd../..------------------------(parent directory

cd/---------------------------(it changes to root directorycd ~-------------------------(it changes to home directory

18. cp

:copy source file to target fileEx

Cp emp1 emp2----------------------(emp1 tp 2 coping

Cp I m1 m2-------------------------(overwrite confirmation? YCp R source directory to target directory-------cp R abc xyz19. mv

: it is used to rename or move fileEx: mv exiting filename new filename

Mv emp .emp----------------------(to hide

Mv .emp emp--------------------(to unhide

20.ls

: display, list of all files & directories in a current directory

21.ls|more

: display, list of all files & directories page by page

22. ls a

: display, list of all files & directories including hidden files and dirctories also in current directory

23. ls r

: display list of all files & directories revers order in a current directory

24. Ls R

: display list of all files & directories recursively in a current directory

25. Ls t

: display list of all files & directories according to date of creation in a current directory

26. Ls F

: display all list of files & directories, link files, .exe files in a current directory

27. Ls-x

: display all list of files & directories according to width wise in a current directory

28. Ls-L

: display all list of files & directories in a current directory in a long list i.e. 9 fields 1) File types

[1) -- For regular file ii) dfor dir file III) Lfor link file IV) bfor block of filesV) c for char files] [here IV, V is device files]2) File permissions 3) no. of links 4) owner name 5) group name 6) file size in bytes 7) Date 8) time 9) filename30. cmp

: it compares two files char by char

Sys: cmp file1 file2 E:\files in ds\In Bound>cmp type1.txt type2.txt

type1.txt type2.txt differr: char 25, line 2 Ex: a1: Hello Good Morning a2: Hello Good Evening

If two lines are same then return nothing If two files are are different then it displays line number with character position31. comm.

: It display common lines b/w 2 files Syn: Comm File1 file2

32. diff

: it display different lines b/w 2 files

33. pg

: it display the file contents page by page

Syn: $Pg filename34. more

: it also display the file contents page by page

Syn: $more filename

34. head :it display the 1st n lines from the file

Sys: $ head n filename

35. tail

: it display the last n lines from file

Syn: tail n filename

Tail +n filename----(it indicates nth line to end of the line Ex: tail +30 file (in this file total no of records is 100) it displays the records from 30th to 100

36. wc

: it counts the no of lines, words, chars in a given file.

Syn: $wc filename

i) wc l filename------------------(it gives the no of lines in a given file

ii) wc w filename---------------(it gives the no of words in a given fileIII) wc c filename---------------( it gives no. of char in file

iv) wc -lw filename--------------( it gives the no of lines and character in a given file

37. WILD CARD CHARCTERS or META CHARCTERSi)*--------(it matches 0 or more chars

ii)? -------(it matches any single chars

iii) [ ] ---(it matches any single chars in the given listiv)------(it matches any single char in the given range

1) ls t*---------------(it list the files starts with t2) ls *s -------------(it list the files that ends with S3) ls b*k--------------(it list the files starts with b and ends with k4) ls a?--------------(it list the 2 characters filename 1st later fallowed by a and second letter is any one character5) ls[bknt]-----------(it list the files starts with b or k or n or t6) ls [abcdefgh] or ls[a-h]*--(list the files, first char b/w a to h7) ls [b-k][p-t][d-n]*---------( it list the files the 1st character b to k 2nd char p to t 3rd char d to n after that any no of charactersls doesnt care about Case sensitive ex: ls [aeiou]*.txt and ls[AEIOU]*.txt both will give the same result38. grep

: [globally search a regular expression and print it]Is used for to search a string or regular expression in a given file(s)

I) Eg: $ grep madhav sample

O/p: 2nd line

5th line

7th line

ii) Eg: $grep madhav a1, a2, a3:

a1:------

a2:------

a3:------

iii) $ grep techno *------(it searches for techno in current dir files (all files)

iv) $grep techno soft sample-----(it searches for more than one word We kept it in

v) $grep techno soft sample

grep cmd options

$ grep i techno sample-----------------------(ignore case sensitive

$ grep c techno sample-----------------------(count no of lines

$grep n techno sample-----------------------(print along with the line numbers

$grep l techno *------------------------------(list only file names

$grep v techno soft sample---------------(not matches print the lines

$grep ci techno sample----------------------(Ignore case sensitive found no of lines

$grep techno * sample---------------------(pattern

Regular expression: any string contains wildcard charctor knows as regular expression or pattern

These patterns are of 3 types:

Charctor pattern: the default pattern is char pattern only

i) $grep techno * sample

ii) $grep b [aeiou] ll sample

iii) $grep b..d sample---(i.e. or matches any single charctor

Word pattern :/< />

/< -------(start of the word

/>------(end of the word

Grep / sample ------------(o/p: technoGrep / sample ----(o/p: hellotechno, abctechnoGrep /< [0-9][0-9][0-9][0-9]/> sample--------------(it display 4 digits (i.e.1234, 4567)

Line pattern: ^----------starts of the file

$----------ends of the file

Ex: grep ^d sample---------------(it display the line starts withd Grep ^the sample-----------------(it list the lines start with the

Grep ^/ simple ----------(sample the line exactly start with the

Grep t$ simple-------------------(list the line ends witht or last char ist2019 Grep [0-9] $ sample------------( display the line ends with 0 to 9 digit

Grep ^ [bkt] sample------------(list the line starting with b or k ortGrep ^ [^bkt] sample----------(list the line which is not start with b or k ortGrep ^UNIX$ sample ---------(display the line having only word Unix

Grep ^. $----------------------(list the line which contains 4 characters (.)----------------------------------(represent single charctor

Grep ^.------------------------(Sample it list all lines

Grep /. Sample: --------------(it lists the line start with (.)

We use \ to search *, $, ^ as a charctor-------( i.e.\*,|^,\$Grep ^$ sample--------------( it list empty lines

Grep c ^$ sample----------(counts no of empty lines in a file

Grep v ^$ sample----------(print not matches (i.e. not empty) linesGrep v ^$sample >tempMv temp sample-------------------(here both are delete empty filesThis command is used to show the After 3 lines when the string is found

Grep A 3 i Chandra emp.txtThis command is used to show the Before 3 lines when the string is found

Grep B 3 I se emp.txt

If the no.of lines found are not exactly same as the lines found then it will result the lines that it found.

39. fgrep: it is used for search multiple strings but it doesnt allow to search regular expression

$grep hello

>techno

>UNIXsample----------(it searches for hello or techno str UNIX40. egrep

: it is combination of grep and fgrep

$egrep hello

>hello

>UNIXsample $egrep ^$ sample

41. Sed

: to replace a string

$ sed s/existing string/new string/g filename--(sed is used to find and replace and grep is for find printHere g is to state that replace existing string with new string Globally. If we want to replace only second instance then

Sed s/ existing string/new string/2We can use any delimiter to replace the command

Sed s| existing string| new string |gWe can replace the string in only one particular line

Sed 3 s| existing string| new string |gWe can replace range of lines by using below command

Sed 1,3 s| existing string| new string |gWe can find any no.of lines 2 times by using sed command

Sed p emp.txt -( This will print all lines 2 times

We can print only particular lines of a file

Sed n 1p;$p emp.txtWe can delete lines by usin sed

Sed 2 d emp.txt (Delete 2 line

Sed 1d; $d emp.txt (Delete 1 and last line

Sed 1,5 d emp.txt (Delete the line range from 1 to 5.i) $sed s/Unix/Linux/gi madhav: -------------( i for case sensitive

ii) $sed s/^Unix/Linux/gi----------------------( whatever lines starting with UNIX are replaced by Linuxiii) $sed s/^$/I like Unix/g I sample--------(empty string are filled with I like UNIXiv) $Sed s/Unix//g I sample-----------------(it search UNIX if found replace with nothing (empty)

42. tr

: to translate a charctor

i) tr a p temp

$mv temp sample

Sorting the data field by field

+pos--(starting field

-Pos--(ending field (optional)

i) Sort f +pas1 pas2 filename

ii) Sort f +1 -3 filename-----(starting from end before 3

iii) Sort fn +2 -3 file ------(it gives only numbers

46) Uniq: it displays unique lines in the given file but the file contents should be in sort order

Ex:file1i) $ uniq file ii) $uniq u filename--(it eliminates duplicates Aaaaaa AaaaaaAaaaaa

cccccAaaaaacccccccc

ddddd

Cccccccdddddd

Ppppp

Ddddd

hhhhhh

ttttttt

Hhhhh

pppppp

Hhhhh

ttttttttt

Ppppp

Ttttttt

iii) $ Uniq d filename----displays only duplicated lines IV) uniq c filename-----(it counts how many times lines duplicated

Aaaaaa-----2

Cccccccc----1

V) $ uniq u file >temp

$ mv temp filename

Delete duplicated lines from file

Ddddd-----1

Hhhhhh---2

Ppppp-----1

Ttttttt-----1

47)piping(|) : it is used for to combine 2 or more cmds |take left side o/p to right side cmd as i/p

i) $who |wc l---------(count total no of lines (files) in current directory

ii) $ ls|wc l------------(displays total no of subdirectories in the current directoryiii) ls l |grep ^d----(displays total no of subdirectories who stats with line nodiV) $head -30 sample|tail +20 sample------(display the the lines from 20 to 30 from given file

v) $ grep UNIX stud | cut f 2, 3|sort filename -----(display UNIX students names & ph no in ascending order

48) $tee

: it is used to for to write data to the file as well as to the screen

$grep UNIX stud | cut f 2, 3 |sort |tee file149) Shell scripting:It is group of UNIX commands and shell keywordsThe main concept of shell scripting is to handle text files

I) Boune shell----(steave Bourne -----($--------sh--- (sh as interpreter)

ii) Bash shell (borne again shell) ---same as above--(advanced version of Bourne is BASH (Linux default shell)iii) Korn shell------David korn----$----------ksh (interpreter) ----(used as AIX default shell

Mostly used shell is korn shell it supports re usability, all shell designed on bourn shell50) $ksh

: shift to korn shell

51) $echo $0 : it displays current child shell name

52) $alias

: it lists all alias names

53) Unalias alias names: to delete alias names54) $ history

: it displays the previously executed commands

55) Echo

: it display the string on screen (monitor)

File permissions:(xxx/xxx/xxx)User/owner---permissions (first part)

Group permissions

(second part)

Other permissions

(third part)

+--- (add permissions to u/g/o but it does not delete exiting permission)

--- (deny permissions)=---- (assign permissions (add permissions to u/g/o but it delete exiting permission))

rw-/rw-/r-- ---------(Default permissions for regular files

rwx/rwx/r-x---------(default permission for directories

56) chmod

: it is used for to change file permissions

Syn: $chmod who/ [+/-/=]/

i) ls l filename-------(rw- rw- r

ii) chmod g+x filename-----(rw- rwx r

iii) chmod u+x, g-w filename------(rwx r-x r

iV) chmod g=w filename-----(rwx w- rOctal code

Read------4

Write-----2

Execute1

$chmod 756 filename-------(rwx r-x rw-

$chmod 642 filename----(rw- r-- -w-57) chown : to change owner name of the file

#chown owner name filename

58) chgrep : to change group name of the file

# chgrp group name filename

58) $write : it is user for to with the users but the user shxould be logged into the server

$write techno2

ii) $mesg n--(deny the msg

Hello

iii) mesg y-(to allow msges

Cmtl+d

59) awk/nawk file

: scan for patterns in a file and process the results

60) cat

: concatenate (list) or file

61) chsh (paawd e/-s) userlogin_shell: change the user login shell

62) df

: report the summary of disk blocks and nodes free and in use

i) df k---(it displays the disk space in bytes ii) df h---(it displays disk space in kilo bytes iii) df g---(it displays the disk space in giga bytes63)du :it displays the directory wise disk usage in form of blocks each block size is 512 bytes64)g zip

:to create a zip file

Ex $gzip filename----(o/p: filename.gzTo Create multiple Zip files to a single Zip file we use below command

>Zip myzip.zip emp*.txtThe above command will zip all the files to Myzip.zip and we can get all files starting with emp.65) gunzip : to unzip the files

Ex: gunzip filename.gz

66. compress: it also used for to zip the file---(it used to save with .z format67) Uncompress: same as above

Gzip saves more memory than compress

68) zcat

: it used to displays zip file contents in readable format$zcat sample.gzOr

$zcat sample.z

69) To kill foreground job cntl+c or cntl+z$ sleep 500

Cntl+c

$ sleep 100&

70) ps or $ ps f : it displays current user account running process list (show status of active process)71) $ps a: it displays all user accounts running process list

72) Kill

: it kill background process

Ex: kill PID73) telnet : to connect to remote server

74) ftp: file transfer protocol -----(transfer files from one server to another

$ ftp ipaddress

Login: -------

Password: ------

Ftp>ls (server)

Ftp>|ls(client)

Ftp>get filename (to download a file)

Ftp>mget file1 file2----- (to download multi files)

Ftp>put filename (to upload a file)Ftp>mput file1 file2----- (to upload multi files)

75)Ftp: to transfer files from one server user account to another server user account

$su root --(to switch to admin

76) Wall

: it is used for to sent broadcast message to all users who are currently working on server

$wall

Happy new-yearCntl+d

77)mail :it is used for to send the mail, if user is not logged in then also we can send mail

i) $ mail techno1

Cntl+d every user contains mailbox

at a time we can send msg to multiple users

2) $mail techno1 techno2 techno 3

Sub: from techno

Cntl+d

iii) $ mail technofirst mail

2>second mail reading

&2 it quickly opens second mail

&q--(quit from mail box

&w to save mail contents to a file

&p(print mail contents

&r--(replays

&d-(delete mails

78)$mail f:to read mails send to secondary mailbox

79) emacs:full screen editor

80) echo: echo the text string to on monitor

81) file : classify the file type

82) expr: evaluates the arguments, used to do arithmetic,etc in the shell

83) find : find files, matching a type or pattern

84) Hostname : display or set the name of the current machine85)ln

: link the source to target86)lpq,lpstat

:show the status of the print jobs

87)lpr,lp

:print to defind printer

88) lprm, cancel: remove a print job from the print quee

89) man

:display manual of given cmd

90)od

:octal dump a binary file,in octal,ASCII,hex,decimal or char

91)passwd

:to set or change password

92) pr

: filter the file and print it on the terminal

93) rcp hostname: remotely copy files from this machine to another machine94) rlogine hostname: login remotely to another machine

95) rsh hostname: remote shell to run on another machine

96) script file

: saves everything that appears on the screen to file until exit is executed

97) source file

: read cmds from the file and execute them in the current shell

98) string file

: used to search binary files for ASCII strings

99) Sty

: set or display terminal control options

100) uudecode file

: decode a uuencoded file, recreating the original file

101) uuencode new name

: encode the binary file to 7-bit ASCII,usefull when sending via email, to be Decode as new name at destination

102) vi

: visual ,full screen editor103) jobs

: display background and suspended processes

104) kill %1

: remove suspended process #1

105) top

: display the current, most computer-intensive commands

106) osview

: display the operating system statistics

107) setenv

: list environmental variables

UNIX

What is meant by passwd file?

This file maintains each and every user information with 7 fields. The 7 fields are Username: passwd: uid: gid: fullname: home: shell.

What is Shell?Shell is a command line interpreter. Shell acts as an interface between user and the kernel.

What is Kernel?

Kernel is core part of UNIX o/s. It is a group of hundreds of system calls.

What are different flavors of Unix o/s?

Any operating system designed based on unix kernel called as flavour of unix. The following are some flavours of unix

Linux ---- Red Hat

Sun solaris --- Sun Microsystem

IBM-AIX ----- IBM

Hp-ux ----- HP

Sco-unix ----- santa crus operations

IRIX------ Silicon Graphics.

What are the different security features in Unix?

1. Password protection.

2. File permissions.

3. Encryption.

Whats the command to find out todays date?

date

Whats the command to find out users on the system?

who

How do you find out the current directory youre in?pwd

What is the command to see the location of command?

Where is

How do you find out your own username?

Whoami (or) log name

How to close the current user account?

Exit

How to create empty file?

Touch

How do you remove a file?

Rm

How to join multifile files vertically?Cat file1 file2 file3

The file for which we do not have write permission can be deleted using the command?

rm -f

How do you remove a directory and its subdirectories?

rm rf

How to rename a file?Mv

How to copy multiple files and directories into some other directory?cp -r source_directory destination_directory

How to see hodden files?

Ls a

How to see files and subdirectories files recursively?

Ls R

How to see files in long list format page wise?Ls l | more

How to identify whether a file is normal file or directory? $ls -l filename/directoryname

if the first digit is - then it is file,

if it is d then it is directory file

What is the difference between "ls -r" and "ls -R"?

ls -r lists the files in reverse alphabetical order... whereas ls -R lists the files and directories recursively

The difference between a soft link and a hard link?A symbolic (soft) linked file and the targeted file can be located on the same or different file system while for a hard link they must be located on the same file system.

what are the different commands used to create files?

1.touch - to create empty files (e.g) - touch

2.vi

3. cat>filename

List some wild card characters?

? -( Iit matches any single character

* -( It matches zero or more characters

[] -( It matches any single character in given list

. -( It matches any single character except enter key character

what is the output of the follwing command : ls [a-mno-r]*

list all the files in the current directory starting alphabet

is between a to m or n or between o to r

How do you count words, lines and characters in a file?

Wc

which command is used to identify the type of the file?file

"grep" means

Globally search a regular expression and print it

How do you search for a string inside a given file?

grep string filenameHow do you search for a string inside a current directory?

grep string *

How do you search for a string in a directory with the subdirectories recursed?

grep -r string *

Difference between grep, egrep and fgrep

grep : does not accept more then one expression

egrep : accepts more than one pattern for search. Also accepts patterns from a file.

fgrep : accepts multiple patterns both from command line and file but does not accept regular expressions only strings. It is faster than the other two and should be used when using fixed strings.

What are line patterns?

^ -( start of the line

$ -( End of the line

How to search empty lines in a given file?

Grep ^$

How to count no of blank lines in a file?

Grep c ^$

How to remove Empty lines form a given file?

Grep v ^$ filename > temfilename

Mv tempfilename filename

What is pattern to search 4 digit word in a file?

Grep \ filename

What is pattern to search the line having only three characters?

Grep ^$ filename

What is pattern to display lines ending with $ character in a given file?

Grep \$$ filename

How to display 2 and 4 th fileds from a given file if the delimetr is :?

Cut d: f 2,4 filename

How to display unique lines from a given file?

Sort u filename

How to eliminate completely duplicate lines from a given file?Uniq u filename

How to remove all duplicate lines from a file?Uniq u filename > tempfilename

Mv tempfilename filename

How to delete hello word from a given file?

Sed s/hello// filename

awk Command

awk is a powful Unix command. It allows the user to manipulate files that are structured as columns of data and

Once you understand the basics of awk you will find that it is surprisingly useful. You can use it to automate things in ways you have never thought about. It can be used for data processing and for automating the application of Unix commands. It also has many spreadsheet-type functionalities.

There are two ways to run awk. A simple awk command can be run from the command line. More complex tasks should be written as awk programs ("scripts") to a file. Examples of each are provided below.

Example: % awk 'pattern {action}' input-file > output-file

meaning: take each line of the input file; if the line contains the pattern apply the action to the line and write the resulting line to the output-file.

If the pattern is omitted, the action is applied to all lines:

How to compare two files are same or not?

Cmp

How to display the first 10 lines from a file?

Head -10 filename

Write a one line command to convert all the capital letters of a file "test" into lower case?

cat filename | tr "[A-Z]" "[a-z]"

The pipeline to list the five largest files in the current directory is

ls -l | tr -s ' ' | sort -t ' ' -fnr +4 -5 | head 5

The pipeline to find out the number of times the character ? occurs in the file is

tr -dc '?' < file | wc -c ( Delete all the characters except ? and then make a word count.)

How to count total no. of users working in the system?

Who | wc l

How to display the lines from 5 to 10 from a given file?

Head -10 filename | tail +5

what will be output of following command?

echo Tecnosoft | wc c

9

What is the default umask?

022

What is the default permission for File & Directory ?

The Default privileges for file : 644

The default privileges for directory : 755

What UNIX command will control the default file permissions when files are created?Umask

Explain the read, write, and execute permissions on a UNIX directory.

Read allows you to see and list the directory contents.

Write allows you to create, edit and delete files and subdirectories in the directory.

Execute gives you the previous read/write permissions plus allows you to change into the directory and execute programs or shells from the directory.

What is chmod, chown and chgrp?

Chmod : It is used for to change permissions on files

Chown : It is used for to change ownership of a file

Chgrp : It is used for to change group of the file

If the owner doesnt have write permission on a file, but his/her group has, can he/she edit it?

No. He/she can't,because the owner's permission overrides the group's.

To see list of files and directories ,what permission required?

Read permission

What are PIDs?

They are process IDs given to processes. A PID can vary from 0 to 65535.

How do you list currently running process?

ps

How do you stop a background process?

kill pidHow do you find out about all running processes?

ps -agHow do you stop all the processes, except the shell window?

kill 0How do you fire a process in the background?

./process-name &

What does the command "kill -9 $! " do?

kills the last background process

if there is a process u want to run even after exiting the shell what is the

command used?

Nohup

which command will get executed even after you log out?

Nohup

which signal cannot be trapped?

kill 9

How to redirect standard error to a file? Answer2> filename

What does the top command display?

top command displays the current ammount of memory occupied

by the currently executing processes and the details. In addition to memory usage top command displays cpu usage and process details

What is the command to send message to all users who are logged in?

Wall

What is the command to send mail to other user?

Mail username

How to open secondary mail box?

Mail -f

What do you do if you don't want to be interrupted by other users' messages?

Ans. mesg n

Shell Scripting Interview questions

Difference between the output of echo ** and echo * *

echo ** lists all the filenames in the current directory..

echo * * lists all the filenames in the current directory twice.

The other way of running shell script apart from using sh command and chmod?

ans:- using ! we can run a shell script

19. How do you refer to the arguments passed to a shell script? - $1, $2 and so on. $0 is your script name.20. Whats the conditional statement in shell scripting? - if {condition} then fi21. How do you do number comparison in shell scripts? - -eq, -ne, -lt, -le, -gt, -ge22. How do you test for file properties in shell scripts? - -s filename tells you if the file is not empty, -f filename tells you whether the argument is a file, and not a directory, -d filename tests if the argument is a directory, and not a file, -w filename tests for writeability, -r filename tests for readability, -x filename tests for executability23. How do you do Boolean logic operators in shell scripting? - ! tests for logical not, -a tests for logical and, and -o tests for logical or.24. How do you find out the number of arguments passed to the shell script? - $#25. Whats a way to do multilevel if-elses in shell scripting? - if {condition} then {statement} elif {condition} {statement} fi26. How do you write a for loop in shell? - for {variable name} in {list} do {statement} done27. How do you write a while loop in shell? - while {condition} do {statement} done28. How does a case statement look in shell scripts? - case {variable} in {possible-value-1}) {statement};; {possible-value-2}) {statement};; esac29. How do you read keyboard input in shell scripts? - read {variable-name}30. How do you define a function in a shell script? - function-name() { #some code here return }31. How does getopts command work? - The parameters to your script can be passed as -n 15 -x 20. Inside the script, you can iterate through the getopts array as while getopts n:x option, and the variable $option contains the value of the entered option.

Batch file:

Batch files allow MS-DOS and Microsoft Windows users to create a lists of commands to run in sequence once the batch file has been executed. For example, a batch file could be used to run frequently run commands, deleting a series of files, moving files, etc. A simple batch file does not require any special programming skills and can be done by users who have a basic understanding of MS-DOS commands.

ORACLE9i FAQs

1.WHAT IS DATA OR INFORMATION?

Ans: The Matter that we feed into the Computer is called Data or Information.

2.WHAT IS DATABASE?

Ans: The Collection of Interrelated Data is called Data Base.

3.WHAT IS A DATABASE MANAGEMENT SYSTEM (DBMS) PACKAGE?

Ans: The Collection of Interrelated Data and some Programs to access

the Data is Called Data Base Management System (DBMS).

4.WHEN CAN WE SAY A DBMS PACKAGE AS RDBMS?

Ans: For a system to Qualify as RELATIONAL DATABASE MANAGEMENT system,

it must use its RELATIONAL facilities to MANAGE the DATABASE.

5.WHAT IS ORDBMS?

Ans: Object (oriented) Relational Data Base Management System is one

that can store data, the relationship of the data, and the behavior of the data

(i.e., the way it interacts with other data).

6.NAME SOME CODD'S RULES.

Ans: Dr. E.F. Codd presented 12 rules that a database must obey if it

is to be considered truly relational. Out those, some are as follows

a)The rules stem from a single rule- the zero rule: For a system to Qualify as RELATIONAL DATABASE MANAGEMENT system, it must use its RELATIONAL facilities

to MANAGE the DATABASE.

b)Information Rule: Tabular Representation of Information.

c)Guaranteed Access Rule: Uniqueness of tuples for guaranteed accessibility.

d)Missing Information Rule: Systematic representation of missing information as NULL Values.

e)Comprehensive Data Sub-Language Rule: QL to support Data definition,

View definition, Data manipulation, Integrity, Authorization and Security.

7.WHAT ARE HIERARCHICAL, NETWORK, AND RELATIONAL DATABASE MODELS?

Ans: a) Hierarchical Model: The Hierarchical Model was introduced in

the Information Management System (IMS) developed by IBM in 1968. In this data is organized as a tree structure. Each tree is made of nodes and branches.

The nodes of the tree represent the record types and it is a collection

of data attributes entity at that point. The topmost node in the structure is called the root. Nodes succeeding lower levels are called children.

b) Network Model: The Network Model, also called as the CODSYL database

structure, is an improvement over the Hierarchical mode, in this model concept of parent and child is expanded to have multiple parent-child relationships, i.e. any child can be subordinate to many different parents (or nodes). Data is represented by

collection of records, and relationships among data are represented by

links. A link is an association between precisely two records. Many-to-many relationships can exists between the parent and child.

c) Relational Model: The Relational Database Model eliminates the need

for explicit parent-child relationships. In RDBMS, data is organized in two-dimensional tables consisting of relational, i.e. no pointers are maintained between tables.

8.WHAT IS DATA MODELING?

Ans: Data Modeling describes relationship between the data objects. The

relationships between the collections of data in a system may be graphically represented using data modeling.

9.DEFINE ENTITY, ATTRIBUTE AND RELATIONSHIP.

Ans: Entity: An Entity is a thing, which can be easily identified. An entity is any object, place, person, concept or activity about which an enterprise records data.

Attribute: An attribute is the property of a given entity.

Relationship: Relationship is an association among entities.

10.WHAT IS ER-MODELING?

Ans: The E-R modeling technique is the Top Down Approach. Entity

relationship is technique for analysis and logical modeling of a systems data requirements. It is the most widely used and has gained acceptance as the ideal database design. It uses three basic units: entities, their attributes and the relationship that exists between

the entities. It uses a graphical notation for representing these.

11.WHAT IS NORMALIZATION?

Ans: Normalization is a step-by-step decomposition of complex records

into simple records.

12.WHAT ARE VARIOUS NORMAL FORMS OF DATA?

Ans: The First Normal Form1NF,

The Second Normal Form2NF,

The Third Normal Form3NF,

The Boyce and Codd Normal FormBC NF.

13.WHAT IS DENORMALIZATION?

Ans: The intentional introduction of redundancy to a table to improve

performance is called DENORMALIZATION.

14.WHAT ARE 1-TIER, 2-TIER, 3-TIER OR N-TIER DATABASE ARCHITECTURES?

Ans: 1-Tier Database Architecture is based on single system, which acts

as both server and client.

2-Tier Architecture is based on one server and client.

3-Tier Architecture is based on one server and client out that on

client act as a remote system.

N-Tier Architecture is based on N no. Of servers and N no. Of clients.

15.WHAT ARE A TABLE, COLUMN, AND RECORD?

Ans: Table: A Table is a database object that holds your data. It is

made up of many columns. Each of these columns has a data type associated with it.

Column: A column, referred to as an attribute, is similar to a field in

the file system.

Record: A row, usually referred to as tuple, is similar to record in

the file system.

16.WHAT IS DIFFERENCE BETWEEN A PROCEDURAL LANGUAGE AND A

NON-PROCEDURAL LANGUAGE?

Ans:

Procedural LanguageNON-Procedural Language

A program in this implements a step-by-step algorithm to solve the

problem. It contains what to do but not how to do .

17.WHAT TYPE OF LANGUAGE "SQL" IS?

Ans: SQL is a Non-procedural, 4th generation Language,/ which concerts

what to do rather than how to do any process.

18.CLASSIFICATION OF SQL COMMANDS?

Ans:

DDL (Data Definition Language)DQL [Data Querying Lnaguage ]

DML (Data Manipulating Language)DCL (Data Control Language)

TCL(Data Transaction Language)

Create Alter Drop Truncate Rename, Select , Insert Update Delete Merge , Grant Revoke , Rollback Commit savepoint

19.WHAT IS DIFFERENCE BETWEEN DDL AND DML COMMANDS?

Ans: For DDL commands autocommit is ON implicitly whereas For DML

commands autocommit is to be turned ON explicitly.

20.WHAT IS DIFFERENCE BETWEEN A TRANSACTION AND A QUERY?

Ans: A Transaction is unit of some commands where as Query is a single

line request for the information from the database.

21.WHAT IS DIFFERENCE BETWEEN TRUNCATE AND DELETE COMMANDS?

Ans: Truncate Command will delete all the records where as Delete

Command will delete specified or all the records depending only on the condition given.

22.WHAT IS DIFFERENCE BETWEEN UPDATE AND ALTER COMMANDS?

Ans: Alter command is used to modify the database objects where as the

Update command is used to modify the values of a data base objects.

23.WHAT ARE COMMANDS OF DCL CATEGORY?

Ans: Grant and Revoke are the two commands belong to the DCL Category.

24.WHICH IS AN EFFICIENT COMMAND - TRUNCATE OR DELETE? WHY?

Ans: Delete is the efficient command because using this command we can

delete only those records that are not really required.

25.WHAT ARE RULES FOR NAMING A TABLE OR COLUMN?

Ans: 1) Names must be from 1 to 30 bytes long.

2) Names cannot contain quotation marks.

3) Names are not case sensitive.

4) A name must begin with an alphabetic character from your database

character set and the characters $ and #.

But these characters are discouraged.

5) A name cannot be ORACLE reserved word.

6) A name must be unique across its namespace. Objects in the name

space must have different names.

7) A name can be enclosed in double quotes.

26.HOW MANY COLUMNS CAN A TABLE HAVE?

Ans: A Table can have 1000 columns.

27.WHAT ARE DIFFERENT DATATYPES SUPPORTED BY SQL?

Ans: Char (size), Nchar (size), Varchar2 (size), Nvarchar2 (size) data

types for character values,

Number (precision, scale), Number, Number (n), Float, Float (binary precision) data types for numerical values, Date data type for date values,

Long, Raw (size), Long Raw, Clob, Blob, Nclob, Bfile for large objects.

28.WHAT IS DIFFERENCE BETWEEN LONG AND LOB DATATYPES?

Ans:

LOBLONG

1) The maximum size is 4GB.

2) LOBs (except NCLOB) can be attributes of an object type.

3) LOBs support random access to data.

4) Multiple LOB columns per table or LOB attributes in an object type.

1) The maximum size is 2GB. 2) LONGs cannot. 3) LONGs support only

sequential access.

4) Only one LONG column was allowed in a table

29.WHAT IS DIFFERENCE BETWEEN CHAR AND VARCHAR2 DATATYPES?

Ans: Varchar2 is similar to Char but can store variable no. Of

characters and while querying the table varchar2 trims the extra spaces from the column and fetches the rows that exactly match the criteria.

30. HOW MUCH MEMORY IS ALLOCATED FOR DATE DATATYPE? WHAT IS DEFAULT

DATE FORMAT IN ORACLE?

Ans: For Date data type oracle allocates 7 bytes Memory.

Default Date Format is: DD-MON-YY.

31.WHAT IS RANGE FOR EACH DATATYPE OF SQL?

Ans:

DatatypeRange

Char Varchar2 Number Float LONG, RAW, LONGRAW Large Objects

(LOBs) 2000 bytes 4000 bytes

Precision 1 to 38 Scale -84 to 127 Precision 38 decimals Or 122 binary

precision 2 GB 4GB

32.HOW TO RENAME A COLUMN?

Ans: We cant rename a Column of a table directly. So we follow the

following steps.

To Rename a Column:

a)Alter the table specifying new column name to be given and data type.

b)Then copy the values in the column to be renamed into new column.

c)drop the old column.

33.HOW TO DECREASE SIZE OR CHANGE DATATYPE OF A COLUMN?

Ans: To Decrease the size of a Data type of a column

i.Truncate the table first.

ii.Alter the table column whose size is to be decreased using the same

name and data type but new size.

34.WHAT IS A CONSTRAINT? WHAT ARE ITS VARIOUS LEVELS?

Ans: Constraint: Constraints are representators of the column to

enforce data entity and consistency.There r two levels

1)Column-level constraints 2)Table-level constraints.

35.LIST OUT ALL THE CONSTRAINTS SUPPORTED BY SQL.

Ans: Not Null, Unique, Check, Primary Key and Foreign Key or Referential Integrity.

36.WHAT IS DIFFERENCE BETWEEN UNIQUE+NOT NULL AND PRIMARY KEY?

Ans: Unique and Not Null is a combination of two Constraints that can be present any number of times in a table and cant be a referential key to any column of an another table where as Primary Key is single Constraint that can be only once for table and can be a referential key to a column of another table becoming a referential integrity.

37.WHAT IS A COMPOSITE PRIMARY KEY?

Ans: A Primary key created on combination of columns is called Composite Primary Key.

38.WHAT IS A CANDIDATE COLUMN? HOW MANY CANDIDATE COLUMNS CAN BE

POSSIBLE PER COMPOSITE PRIMARY KEY?

Ans: It is a part of composite primary key. Maximum 32 candidate key can be there in composite primary key.

39.HOW TO DEFINE A NULL VALUE?

Ans: A NULL value is something which is unavailable, it is neither zero

nor a space and any mathematical calculation with NULL is always NULL.

40. WHAT IS NULL? A CONSTRAINT OR DEFAULT VALUE?

Ans: It is a default value.

41. WHAT IS DEFAULT VALUE FOR EVERY COLUMN OF A TABLE?

Ans: NULL.

42. WHAT IS CREATED IMPLICITLY FOR EVERY UNIQUE AND PRIMARY KEY

COLUMNS?

Ans: Index.

43. WHAT ARE LIMITATIONS OF CHECK CONSTRAINT?

Ans: In this we can't specify Pseudo Columns like sysdate etc.

44. WHAT IS DIFFERENCE BETWEEN REFERENCES AND FOREIGN KEY CONSTRAINT?

Ans: References is used as column level key word where as foreign key

is used as table level constraint.

45. WHAT IS "ON DELETE CASCADE"?

Ans: when this key word is included in the definition of a child table

then whenever the records from the parent table is deleted automatically the respective values in the child table will be deleted.

46. WHAT IS PARENT-CHILD OR MASTER-DETAIL RELATIONSHIP?

Ans: A table which references a column of another table(using References)is called as a child table(detail table) and a table which is being referred is called Parent (Master) Table .

47. HOW TO DROP A PARENT TABLE WHEN ITS CHILD TABLE EXISTS?

Ans: Using "on delete cascade".

48. IS ORACLE CASE SENSITIVE?

Ans: NO

49. HOW ORACLE IDENTIFIES EACH RECORD OF TABLE UNIQUELY?

Ans: By Creating indexes and reference IDs.

50. WHAT IS A PSEUDO-COLUMN? NAME SOME PSEUDO-COLUMNS OF ORACLE?

Ans: Columns that are not created explicitly by the user and can be

used explicitly in queries are called Pseudo-Columns.

Ex:currval,nextval,sysdate,new,old,sqlcode,sqlerrm,rownum,rowid,level

51. WHAT FOR "ORDER BY" CLAUSE FOR A QUERY?

Ans: To arrange the query result in a specified

Order (ascending,descending) by default it takes ascending order.

52. WHAT IS "GROUP BY" QUERIES?

Ans: To group the query results based on condition.

53. NAME SOME AGGREGATE FUNCTIONS OF SQL?

Ans: AVG, MAX, SUM, MIN,COUNT.

54. WHAT IS DIFFERENCE BETWEEN COUNT (), COUNT (*) FUNCTIONS?

Ans: Count () will count the specified column whereas count (*) will

count total no. of rows in a table.

55. WHAT FOR ROLLUP AND CUBE OPERATORS ARE?

Ans: To get subtotals and grand total of values of a column.

56. WHAT IS A SUB-QUERY?

Ans: A query within a query is called a sub query where the result of

inner query will be used by the outer query.

57. WHAT ARE SQL OPERATORS?

Ans: Value (), Ref () is SQL operator. ( Used with Objects )

58. EXPLAIN "ANY","SOME","ALL","EXISTS" OPERATORS?

Ans: Any: The Any (or its synonym SOME) operator computes the lowest

value from the set and compares a value to each returned by a sub query.

All: ALL compares a value to every value returned by SQL.

Exists: This operator produces a BOOLWAN results. If a sub query

produces any result then it evaluates it to TRUE else it evaluates it to FALSE.

59. WHAT IS A CORRELATED SUB QUERY, HOW IT IS DIFFERENT FROM A NORMAL

SUB QUERY?

Ans: A correlated subquery is a nested subquery, which is executed once

for each Candidate row by the main query, which on execution uses a value from a column in the outer query. In normal sub query the result of inner query is dynamically substituted in the condition of the outer query where as in a correlated subquery, the column

value used in inner query refers to the column value present in the

outer query forming a correlated subquery.

60. WHAT IS A JOIN - TYPES OF JOINS?

Ans: A join is used to combine two or more tables logically to get

query results.

There are four types of Joins namely

EQUI Join

NON-EQUI Join

SELF Join

OUTER Join.

61. WHAT ARE MINIMUM REQUIREMENTS FOR AN EQUI-JOIN?

Ans: There shold be atleast one common column between the joining tables.

62. WHAT IS DIFFERENCE BETWEEN LEFT, RIGHT OUTER JOIN?

Ans:If there r any values in one table that do not have corresponding values in the other,in an equi join that row will not be selected.Such rows can be forcefully selected by using outer join symbol(+) on either of the sides(left or right) based on the requirement.

63. WHAT IS DIFFERENCE BETWEEN EQUI AND SELF JOINS?

Ans: SELF JOIN is made within the table whereas

EQUI JOIN is made between different tables having common column.

64. WHAT ARE "SET" OPERATORS?

Ans: UNION ALL,UNION, INTERSECT ,MINUS are SET OPERATORS.

65. WHAT IS DIFFERENCE BETWEEN "UNION" AND "UNION ALL"

OPERATORS?

Ans: UNION will return the values distinctly whereas UNION ALL will

return even duplicate values.

66. NAME SOME NUMBER, CHARACTER, DATE, CONVERSION, OTHER

FUNCTIONS.

Ans: Number Functions:

Round (m, [n]), Trunc (m, [n]), Power (m, n), Sqrt(n),

Abs (m), Ceil (m), Floor (m), Mod (m, n) ,sign(n)

Character Functions:

Chr (x), Concat (string1, string2), Lower (string)

Upper (string), Substr (string, from_str, to_str), ASCII (string)

Length (string), Initcap (string).

Date Functions:

Sysdate, Months between (d1, d2), To_char (d, format)

Last day (d), Next_day (d, day).add_months(d,n), Extract

Conversion Functions: To_char, To_date, To_number

67. WHAT IS DIFFERENCE BETWEEN MAX () AND GREATEST () FUNCTIONS?

Ans: MAX is an aggregate function which takes only one column name of a table as parameter whereas Greatest is a general function which can take any number of values and column names from dual and table respectively.

68. WHAT FOR NVL () FUNCTION IS?

Ans: NVL Function helps in substituting a value in place of a NULL.

69. WHAT FOR DECODE () FUNCTION IS?

Ans: It is substitutes value basis and it actually does an

'if-then-else' test.

70. WHAT IS DIFFERENCE BETWEEN TRANSLATE () AND REPLACE () FUNCTIONS?

Ans: Translate() is a superset of functionality provided by Replace().

71. WHAT IS DIFFERENCE BETWEEN SUBSTR () AND INSTR () FUNCTIONS?

Ans: Substr() will return the specified part of a string whereas

Instr() return the position of the specified part of the string.

72. WHAT IS A JULIAN DAY NUMBER?

Ans: It will return count of the no. Of days between January 1, 4712 BC

and the given date.

73. HOW TO DISPLAY TIME FROM A DATE DATA?

Ans: By using time format as 'hh [hh24]: mi: ss' in to_char() function.

74. HOW TO INSERT DATE AND TIME INTO A DATE COLUMN?

Ans: By using format 'dd-mon-yy hh [hh24]: mi: ss' in to_date() function.

75. WHAT IS DIFFERENCE BETWEEN TO_DATE () AND TO_CHAR () CONVERSION

FUNCTIONS?

Ans: To_date converts character date to date format whereas

To_char function converts date or numerical values to characters.

76. WHAT IS A VIEW? HOW IT IS DIFFERENT FROM A TABLE?

Ans: View is database object, which exists logically but contains no

physical data and manipulates the base table.

View is saved as a select statement in the database and contains no

physical data whereas Table exists physically.

77. WHAT IS DIFFERENCE BETWEEN SIMPLE AND COMPLEX VIEWS?

Ans: Simple views can be modified whereas Complex views (created based

on more than one table) cannot be modified.

78. WHAT IS AN INLINE VIEW?

Ans: Inline view is basically a subquery with an alias that u can use

like a view inside a SQL statement. It is not a schema object like SQL-object.

79. HOW TO UPDATE A COMPLEX VIEW?

Ans: Using 'INSTEAD OF' TRIGGERS Complex views can be Updated.

80. WHAT FOR "WITH CHECK OPTION" FOR A VIEW?

Ans: "WITH CHECK OPTION" clause specifies that inserts and updates r performed through the view r not allowed to create rows which the view cannot select and therefore allows integrity constraints and data validation checks to be enforced on data being inserted or updated.

81. WHAT IS AN INDEX? ADVANTAGE OF AN INDEX

Ans: An Index is a database object used n Oracle to provide quick

access to rows in a table. An Index increases the performance of the database.

82. WHAT IS A SEQUENCE? PSEUDO-COLUMNS ASSOCIATED WITH SEQUENCE?

Ans: Sequence is a Database Object used to generate unique integers to use as primary keys. Nextval, Currval are the Pseudo Columns associated with the sequence.

**83. WHAT IS A CLUSTER? WHEN TO USE A CLUSTER? HOW TO DROP A CLUSTER

WHEN CLUSTERED TABLE EXISTS?

Ans: Cluster and Indexes are transparent to the user. Clustering is a

method of storing tables that are intimately related and are often joined together into the same area on the disk.

When cluster table exists then to drop cluster we have to drop the table first then only cluster is to be dropped.

84. WHAT IS A SNAPSHOT OR MATERIALIZED VIEW?

Ans: Materialized views can be used to replicate data. Earlier the data

was replicated through CREATE SNAPSHOT command. Now CREATE MATERIALIZED VIEW can be used as synonym for CREATE SNAPSHOT. Query performance is improved using the materialized view as these views pre calculate expensive joins and aggregate operations on the table.

85. WHAT IS A SYNONYM?

Ans: A Synonym is a database object that allows you to create alternate names for Oracle tables and views. It is an alias for a table, view, snapshot, sequence, procedure, function or

package.

86. WHAT IS DIFFERENCE BETWEEN PRIVATE AND PUBLIC SYNONYM?

Ans: Only the user or table owner can reference Private synonym whereas

any user can reference the Public synonym.

87. WHAT IS DIFFERENCE BETWEEN "SQL" AND "SQL*PLUS" COMMANDS?

Ans: SQL commands are stored in the buffer whereas SQL*PLUS are not.

**88. NAME SOME SQL*PLUS COMMANDS?

Ans:DESC [CRIBE], START, GET, SAVE, / are SQL*PLUS COMMANDS.

89. WHAT ARE "SQL*PLUS REPORTING" COMMANDS?

Ans: SPOOL file-name, SPOOL OFF, TTITLE, BTITLE, BREAK ON, COMPUTE OF [break] ON etc are SQL*PLUS REPORTING COMMANDS.

90. WHAT ARE SYSTEM AND OBJECT PRIVILEGES?

Ans: Connect and Resource etc are System Privileges.

Create , Select, Insert, Alter etc are Object Privileges.

91. WHAT FOR DCL COMMANDS ARE?

Ans: Commit, Rollback are DCL commands.

92. WHAT FOR GRANT COMMAND WITH "WITH GRANT OPTION"?

Ans: With Grant Option with Grant Command gives privileges to the

user to grant privileges to other user(s)

among the privileges he/she has.

93. HOW TO CHANGE PASSWORD OF A USER?

Ans: Using Password command or

Using ALTER USER IDENTIFIED BY COMAND.

94. WHAT IS A SCHEMA AND SCHEMA OBJECTS?

Ans: A schema is a collection of logical structures of data, or schema

objects. A schema is owned by the database user and has the same name as that of user. Each user owns a single schema. Schema objects include following

type of objects Clusters, Database Links, Functions, Indexes, Packages,

Procedures, Sequences, Synonyms, Tables, Database Triggers, Views.

**95. HOW TO STARTUP AND SHUTDOWN ORACLE DATABASE?

Ans: Startup and Shutdown Oracle database can be done by only the

administator. Startup is done by using STARTUP command and Shutdown is done by SHUTDOWN command

96. WHAT IS A SESSION?

Ans: The period between Login and Logoff on schema.

97. WHAT IS A CLIENT PROCESS? WHAT IS A SERVER PROCESS?

Ans: ref: 172 Q & A.

98. HOW TO MAKE EVERY DML OPERATION AS AUTO COMMIT?

Ans: By using SET AUTOCOMMIT ON command.

99. HOW TO DISPLAY DATA PAGE WISE IN SQL?

Ans: By using SET PAUSE ON command.

100. HOW TO CHANGE LINE SIZE, PAGE SIZE AND SQL PROMPT?

Ans: By using SET LINESIZE , SET PAGESIZE ,

SET SQLPROMPT .

101. HOW PL/SQL IS DIFFERENT FROM SQL?

Ans: SQL is non-procedural language whereas PL/SQL is procedural

language that includes features and design of programming language.

102. WHAT IS ARCHITECTURE OF PL/SQL?

Ans: Give picture & Explain

103. WHAT IS A PL/SQL BLOCK?

Ans:DECLARE

BEGIN

EXCEPTION

END;

104. WHAT ARE DIFFERENT TYPES OF PL/SQL BLOCKS?

Ans: DECLARE BLOCK: In this block all the declarations of the variable

used in the program is made. If no variables are used this block will become optional.

BEGIN BLOCK: In this block all the executable statements are

placed. This block is Mandatory.

EXCEPTION BLOCK: In this block all the exceptions are handled.

This block is also very optional.

END: Every begin must be ended with this END; statement.

Anonymous & Named Blocks

105. WHAT ARE COMPOSITE DATA TYPES?

Ans: Records, Tables are two Composite data types.

106. WHAT IS SCOPE OF A VARIABLE IN PL/SQL BLOCK?

Ans: The visuability and accessibility of a variable within the

block(s) is called scope of a variable.

107. WHAT IS A NESTED BLOCK?

Ans: A block within a block is called Nested Block.

108. WHAT IS A PL/SQL ENGINE?

Ans: The PL/SQL engine accepts any valid PL/SQL block as input, executes the procedural part of the statements and sends the SQL statements to the SQL statement executor in the Oracle server.

109. WHAT IS DEFAULT VALUE FOR A NUMERIC PL/SQL VARIABLE?

Ans: NULL

110. WHAT IS DIFFERENCE BETWEEN SIMPLE LOOP AND A FOR LOOP?

Ans: Simple requires declaration of variables used in it and exit

condition but For Loop doesnt require this.

111. WHAT IS A CURSOR? STEPS TO USE A CURSOR?

Ans: Cursor is Private SQL area in PL/SQL.

Declare the Cursor,

Open the Cursor,

Fetch values from SQL into the local Variables,

Close the Cursor.

112. HOW MANY TYPES OF CURSORS ARE SUPPORTED BY ORACLE?

Ans: There are two types of cursors namely Implicit Cursor, Explicit Cursor.

113. WHAT IS A CURSOR FOR LOOP?

Ans: Cursor For Loop is shortcut process for Explicit Cursors because

the Cursor is Open, Rows are fetched once for each iteration and the cursor is closed automatically when all the rows have been processed.

114. WHAT ARE CURSOR ATTRIBUTES?

Ans: %Found

%NotFound

%IsOpen

%RowCount are the cursor attributes.

115. WHAT IS USE OF CURSOR WITH "FOR UPDATE OF" CLAUSE?

Ans: This Clause stop accessing of other users on the particular

columns used by the cursor until the COMMIT is issued.

116. WHAT IS AN EXCEPTION? HOW IT IS DIFFERENT FROM ERROR?

Ans: Whenever an error occurs Exception raises. Error is a bug whereas the Exception is a warning or error condition.

117. NAME SOME BUILT-IN EXCEPTIONS.

Ans: Too_Many_Rows, No_Data_Found, Zero_Divide, Not_Logged_On

Storage_Error, Value_Error etc.

118. HOW TO CREATE A USER-DEFINED EXCEPTION?

Ans: User-Defined Exception is created as follows:

DECLARE

EXCEPTION;

- - - - - - - - - ;

- - - - - - - - -;

BEGIN

- - - - - - - - -;

- - - - - - - - -;

RAISE ;

EXCEPTION

WHEN THEN

- - - - - - - - -;

- - - - - - - - -;

END;

119. WHAT IS "OTHERS" EXCEPTION?

Ans: It is used to along with one or more exception handlers.

This will handle all the errors not already handled in the block.

120. WHAT IS SCOPE OF EXCEPTION HANDLING IN NESTED BLOCKS?

Ans: Exception scope will be with in that block in which exception

handler is written.

121. WHAT IS A SUB-PROGRAM?

Ans: A SUBPROGRAM IS A PL/SQL BLOCK, WHICH WILL BE INVOKED BY TAKING

PARAMATERS.

122. WHAT ARE DIFFERENT TYPES OF SUB-PROGRAMS?

Ans: THEY R TWO TYPES: 1) PROCEDURE 2) FUNCION.

123. HOW A PROCEDURE IS DIFFERENT FROM A FUNCTION?

Ans: Function has return key word and returns a value whereas a

Procedure doesnt return any value.

124. WHAT ARE TYPES OF PARAMETERS THAT CAN BE PASSED TO FUNCTION OR

PROCEDURE?

Ans: IN, IN OUT, OUT.

125. WHAT IS "IN OUT" PARAMETER?

Ans: A parameter, which gets value into the Procedure or Function and

takes the value out of the Procedure or

Function area, is called IN OUT parameter.

126. DOES ORACLE SUPPORTS PROCEDURE OVERLOADING?

Ans: NO.

127. WHAT IS A PACKAGE AND PACKAGE BODY?

Ans: Package is declarative part of the functions and procedures stored

in that package and package body is

the definition part of the functions and procedures of that package.

128. WHAT IS ADVANTAGE OF PACKAGE OVER PROCEDURE OR FUNCTION?

Ans: Packages provides Functions or Procedures Overloading facility and

security to those Functions or

Procedures.

129. IS IT POSSIBLE TO HAVE A PROCEDURE AND A FUNCTION WITH THE SAME

NAME?

Ans: NO if it is out side a Package, YES if it is within a Package.

130. DOES ORACLE SUPPORTS RECURSIVE FUNCTION CALLS?

Ans: YES.

131. WHAT IS A TRIGGER? HOW IT IS DIFFERENT FROM A PROCEDURE?

Ans: Trigger: A Trigger is a stored PL/SQL program unit associated

with a specific database table.

Procedure: A Procedure is to be explicitly called by the user

whereas Triggers are automatically called implicitly

by Oracle itself whenever event Occurs.

132. WHAT IS DIFFERENCE BETWEEN A TRIGGER AND A CONSTRAINT?

Ans: Constraints are always TRUE whereas Triggers are NOT always TRUE

and Constraints has some limitations whereas Trigger has no limitations.

133. WHAT ARE DIFFERENT EVENTS FOR A TRIGGER AND THEIR SCOPES?

Ans: Insert, Update or Delete.

134. WHAT IS DIFFERENCE BETWEEN TABLE LEVEL AND ROW LEVEL TRIGGERS?

Ans: Table level Triggers execute once for each table based transaction

whereas Row level Triggers will execute once FOR EACH ROW.

** 135. WHAT ARE AUTONOMOUS TRIGGERS?

Ans: Supports to provide Commit statement in Triggers. Triggers a declared as independent

Transactions.

136. WHAT IS AN "INSTEAD OF" TRIGGER?

Ans: These Triggers are used with the Complex Views only to make

possible of Insert, Update and Delete on those Views.

** 137. HOW MANY TRIGGERS CAN BE CONFIGURED ON A TABLE AND VIEW?

Ans: 18 Triggers

138. WHAT IS "TABLE MUTATING" ERROR? HOW TO SOLVE IT?

Ans: ORA-04091:Table name is mutating, trigger/function may not see it

Cause : A trigger or a user-defined PL/SQL function that is referenced

in the statement attempted to query or modify a table that was in the middle of being modified by the statement that fired the trigger.

Action : Rewrite the trigger or function so it does not read the table.

139. WHEN TO USE ":NEW" AND ":OLD" SPECIFIERS?

Ans: The prefix :old is used to refer to values already present in the

table. The prefix :new is a correlation name that refers to the new value that is inserted / updated.

** 141. HOW TO CREATE A USER-DEFINED VARIABLE IN PL/SQL?

Ans: Define variable in declaration section

142. HOW TO CREATE AN ARRAY VARIABLE IN PL/SQL?

Ans: Using CREATE [OR REPLACE] TYPE

AS VARRAY (size) OF ELEMENT_TYPE (NOT NULL) Command;

**143. HOW TO MAKE A USER-DEFINED DATA TYPE GLOBAL IN PL/SQL?

Ans: Declare the variable in a Package

144. HOW TO CREATE AN OBJECT IN ORACLE?

Ans: Using CREATE [OR REPLACE] TYPE AS OBJECT (ATTRIBUTE

NAME DATA TYPE,..) Command

145. WHAT IS A TRANSIENT AND PERSISTENT OBJECT?

Ans: The Object created in a table is called Persistent Object.

Object created on execution of PL/SQL block is called Transient Object.

**146. WHAT IS A COLUMN OBJECT AND TABLE OBJECT?

Ans: A Column Object is only a Column of a table.

147. HOW TO GRANT PERMISSION ON AN OBJECT TO OTHER USER?

Ans: GRANT ON TO .

148. WHAT IS A COLLECTION OF ORACLE?

Ans: Varray, Nested Table is a collection of Oracle.

149. WHAT IS DIFFERENCE BETWEEN VARRAY AND NESTED TABLE?

Ans: Varray has a fixed size.

Nested tables can carry any number of values.

150. HOW TO MODIFY CONTENTS OF A VARRAY IN ORACLE?

Ans: To modify a stored VARRAY it has to selected into a

PL/SQL variable and then inserted back into the table.

151. WHAT IS USE OF "THE" OPERATOR FOR NESTED TABLE?

Ans: THE operator allows nested tables to be manipulated using DML when

it is stored in a Table.

152. WHICH PACKAGE IS USED FOR FILE INPUT/OUTPUT IN ORACLE?

Ans: UTL_FILE Package is used for File input/output in Oracle.

153. NAME SOME METHODS AND PROCEDURES OF FILE I/O PACKAGE?

Ans: FOPEN, FCLOSE, FFLUSH, IS_OPEN, GET_LINE, PUT_LINE, PUTF, NEW_LINE

**154. WHAT IS SQLJ? HOW IT IS DIFFERENT FROM JDBC CONNECTIVITY?

Ans: SQLJ is basically a Java program containing embedded static SQL

statements that are compatible with Java design philosophy.

155. WHAT IS AN ITERATOR? Name some TYPES OF ITERATORS?

Ans: SQLJ Iterators are basically record groups generated during

transaction, which requires manipulation of more than one records from one or more tables. There are two types Iterators namely Named Iterator and Positional Iterator.

** 156. WHAT ARE DIFFERENT STEPS TO WRITE A DYNAMIC SQL PROGRAM?

Ans: Eg: char c_sqlstring[]={DELETE FROM sailors WHERE rating>5};

EXEC SQL PREPARE readytogo FROM :c_sqlstring;

EXEC SQL EXECUTE readytogo;

157. WHAT IS TABLE PARTITIONING AND INDEX PARTITIONING?

Ans: Oracle8 allows tables and Indexes to be partitioned or broken up into smaller parts based on range of key values. Partitioning is a divide and conquer strategy that improves administration and performance in data warehouse and OLTP systems.

159. WHAT IS PHYSICAL MEMORY STRUCTURE OF ORACLE?

Ans: The basic oracle memory structure associated with Oracle includes:

Software Code Areas The System Global Area (SGA) ,The Database Buffer Cache

The shared Pool, The Program Global Areas (PGA), Stack Areas ,Data Areas, Sort Areas

160. WHAT IS LOGICAL MEMORY STRUCTURE OF ORACLE?

Ans: Database, Tablespace , DB Object, Segment, Extents

161. WHAT IS SGA?

Ans: A System Global Area is a group of shared memory allocated by

Oracle that contains data and control information for one Oracle database instance. IF the multiple users are concurrently connected to the same instance, the data in the instances SGA is shared among the users.

Consequently, the SGA is often referred to as either the system Global Area or the Shared

Global Area.

162. WHAT IS PGA?

Ans: The Program Global Area is a memory buffer that contains data and

control information for a server process. A PGA is created by Oracle when a server process is started. The information in a PGA depends on the configuration of Oracle.

163. WHAT IS AN ORACLE INSTANCE?

Ans: Every time a database is started, an SGA is allocated and Oracle

background processes are started. The combination of these processes and memory buffers is called an Oracle instance.

164. WHAT ARE DIFFERENT ORACLE PROCESSES?

Ans: A process is a thread of control or a mechanism in an operating

system that can be execute a series of steps. Some operating systems use terms jobs or

task. A process normally has its own private memory area in which it runs. An Oracle database system has general types of process: User Processes and Oracle Processes.

**165. WHAT IS DIFFERENCE BETWEEN PMON AND SMON?

Ans: SMON (System Monitor) performs instance recovery at instance of

startup. In a multiple instance system (one that uses the parallel server), SMON of one instance can also perform instance recovery other instance that have failed whereas The PMON (Process Monitor) performs process recovery when a user process fails.

**166. WHAT IS DIFFERENCE BETWEEN DATABASE AND TABLESPACE?

Ans: Database is a physical Component

Tablespace is a Logical component

167. WHAT IS JOB OF DATABASE WRITER (DBWR) PROCESS?

Ans: The Data Base Writer writes modified blocks from the database

buffer cache to the data files.

168. WHAT IS JOB OF LOG WRITER (LGWR) PROC*SS?

Ans: The Log Writer writes redo log files to disk. Redo log data is

generated in the redo log buffer of the SGA. As transactions commit and log buffer fills, LGWR writes redo entries into an online redo log file.

169. WHAT IS RECOVERER?

Ans: The Recover (RECO) is used to resolve distributed transactions that are pending due to network or system failure in a distributed database. At timed intervals, the local RECO attempts to concept to remote database and automatically complete the commit or rollback of the local portion of any pending distributed transactions.

170. WHAT IS ARCHIVER?

Ans: The Archiver (ARCH) copies the online redo log files to archival storage when they are full. ,ARCH is active only when a databases redo log is used ARCHILOG mode.

** 171. WHAT IS A STORED QUERY?

Ans: VIEW

172. WHAT IS USER PROCESS AND SERVER PROCESS?

Ans: A User process is created and maintained to execute the software

code of an application program (such as PRO * Program) or an ORACLE tool (such as SQL * DBA). The User process also manages the communication

with server processes. User processes communication with the server

Processes through the program interface.

Other processes call ORACLE processes. In a dedicated server

configuration, a server Process handles requests for a single user process. A multithread

server configuration allows many user processes to share a small number of server processes, minimizing the utilization of available system resources.

**173. WHAT IS A SELF REFERENTIAL INTEGRITY?

Ans: Table related to itself .Foreign key of the table links to primary key of the same table.

174. WHAT IS A "RAISE" STATEMENT?

Ans: It is used to Raise Exceptions.

175. WHAT IS ROWID? HOW IT IS DIFFERENT FROM ROWNUM?

Ans: Rowid is the address of the row at where it is stored in the

database. Rownum is count of records whereas Rowid is identification of the each row.

*** All The Best - SRIDHAR ***

9i features:

9i Joins:

Supports ANSI/ISO standard Sql 1999 syntax

Made easy for Appln s/w tools to understand Sql Queries

1. Natural Join

5. Left outer join

2. Join with Using6. Right outer join

3. Join with ON

*7. Full outer join

4. Inner Join

8. Cross join

1. > select empno,ename,sal,job,deptno,dname,loc

from emp natural join dept;


from emp join dept using(deptno);

3. > select e.empno, e.ename, e.sal, e.job, e.deptno,d.dname, d.loc from emp e Join dept d

on(e.deptno = d.deptno) ;

4. > select e.empno, e.ename, e.sal, e.job, e.deptno, d.dname, d.loc from emp e Inner Join dept d


5. > select e.empno, e.ename, e.sal, e.job, e.deptno, d.dname, d.loc from emp e left outer join dept d


6. > select e.empno, e.ename, e.sal, e.job, e.deptno,d.dname, d.loc from emp e right outer join dept d


* 7. > select e.empno, e.ename, e.sal, e.job, e.deptno,d.dname, d.loc from emp e full outer join dept d


** left outer join union right outer join = full outer join


from emp cross join dept;

----------------------------------------------------------------------------

New Date Functions:

* Systimestamp : Gives date and time including fractional seconds in SERVER time zone

* current_timestamp: Gives date and time including fractional seconds in CLIENT time zone

* sysdate: Gives only date in server time zone

* current_date: Gives only date in client time zone

* Extract : Used to retrieve a particular value from the given date ( day / month / year ).

* to_timestamp(d) : Converts given date into date & time information with am / pm .

* dbtimezone : Gives server time zone value

* Timestamp : Data type

Automatically stores date and time information with am / pm .

>select systimestamp , current_timestamp from dual;

>select sysdate,current_date from dual;

>select dbtimezone from dual;

>select to_timestamp(sysdate) from dual;

20-jan-09 6:48:23 pm

>select extract(day from sysdate) ,

extract(month from sysdate),

extract(year from sysdate) from dual;

create table temp (c1 timestamp);

> insert into temp values(sysdate);

> select * from temp;

20-jan-09 6:52:23 pm

----------------------------------------------------------------------------

New General Functions:

* Coalesce(expr1,expr2,expr3,.......) --- Picks the first not null expression result .

*nullif ( expr1,expr2 ) --- If expr1 and expr2 results are same it returns NULL value otherwise it return expr1 result.

* Nvl2(expr1,expr2,expr3) --- If expr1 is null it manipulates expr3 ,if expr1 is not null it manipulates expr2.

>select coalesce(100 + null, 128 - null + 1000, 12 * null,

225, 2345,9889) from dual; -- 225

>select ename, job, coalesce (comm * 2, sal * 1.5) bonus

from emp;

>select nullif(100,50* 2), nullif(300,30 * 100),

nullif (600,300 + 300) from dual; -- null 300 null

>select roll, name, nullif(fee,2500) from student

where course = 'Oracle9i';

>select ename, job, nvl2(comm,sal + comm,sal) net from emp;

---------------------------------------------------------------------------

Mutiple Inserts:

Supports to insert into more than 1 table at a time.

But input must be retrieved from existing table.

Ex: Make 3 empty tables same as Dept table.

Create table D1 as select * from dept

where rownum is null;





insert into D1 select * from dept;



insert all

into D1 values(deptno,dname,loc)



select * from dept;

Conditional Insert:

insert all

when (deptno