pl/sql and chapter 10 selected single-row functions

Dr. Chen, Oracle Database System (Oracle) 1

PL/SQL andChapter 10

Selected Single-Row FunctionsJason C. H. Chen, Ph.D.

Professor of MISSchool of Business

Gonzaga UniversitySpokane, WA 99258 USA

[email protected]


Objectives• Use the UPPER, LOWER, and INITCAP functions to change the case

of field values and character strings• Manipulate character substrings with the SUBSTR and INSTR

functions• Nest functions inside other functions• Determine the length of a character string using the LENGTH function• Use the LPAD and RPAD functions to pad a string to a certain width• Use the LTRIM and RTRIM functions to remove specific characters

strings• Substitute character string values with the REPLACE and

TRANSLATE functions• Round and truncate numeric data using the ROUND and TRUNC

functions• Return the remainder only of a division operation using the MOD function• Use the ABS function to set numeric values as positive


Objectives (continued)• Use the POWER function to raise a number to a specified power• Calculate the number of months between two dates using the

MONTHS_BETWEEN function• Manipulate date data using the ADD_MONTHS, NEXT_DAY,

LAST_DAY, and TO_DATE functions• Differentiate between CURRENT_DATE and SYSDATE values• Extend pattern matching capabilities with regular expressions• Identify and correct problems associated with calculations involving

NULL values using the NVL function• Display dates and numbers in a specific format with the TO_CHAR

function• Perform condition processing similar to an IF statement with the

DECODE function• Use the SOUNDEX function to identify character phonetics• Convert string values to numeric with the TO_NUMBER function• Use the DUAL table to test functions • Learn PL/SQL – Procedure Language / SQL


Refresh the Database

• 1. Run the following script file– Start c:\oradata\chapter10\JLDB_Build_10.sql

• 2. Download data file, Ch10queries.sql


Functions Must Study and Understand

The following functions are the “minimum” to study and understand:

• 1. Case conversion functions• 2. character manipulation functions

– SUBSTR, INSTR, LENGTH, LTRIM, RTRIM, REPLACE, CONCAT

• 3. ALL Number functions• 4. DATE functions

– MONTH_BETWEEN, ADD_MONTHS, TO_DATE, SYSDATE• 5. Other functions

– NVL, TO_CHAR, CASE, TO_NUMBER, DUAL table


Refresh the Database

• 1. Go to Blackboard and download (at least three) data files from Oracle chapter10 and save under c:\oradata\chapter10\– Please note that there is a PL/SQL data file of

“Ch10 Queries for PL SQL.sql”

• 2. Run the following script file– Start c:\oradata\chapter10\JLDB_Build_10.sql


Manipulating Character Strings with PL/SQL

• To change case, use UPPER, LOWER, INITCAP• INSTR function searches a string for a specific

substring and return the starting positionstart_position := INSTR(original_string, substring,

starting_pos, occurrence#);– /* the first two arguments are required, the last two

arguments are optional */• SUBSTR function extracts a specific number of

characters from a character string, starting at a given point:extracted_string := SUBSTR(string_variable,

starting_point, number_of_characters);


Case Conversion Functions

• Case conversion functions alter the case of data stored in a column or character string– Used in a SELECT clause, they alter the

appearance of the data in the results– Used in a WHERE clause, they alter the value

for comparison


LOWER Function

• Used to convert characters to lowercase letters

Figure 10-1 LOWER function in the WHERE clause


LOWER Function (cont.)• Used to convert characters to mixed case

Figure 10-2 LOWER function in the SELECT and WHERE clauses


UPPER Function

• Used to convert characters to uppercase letters• It can be used in the same way as the LOWER

function– To affect the display of characters, it is used in

a SELECT clause – To modify the case of characters for a search

condition, it is used in a WHERE clause • The syntax for the UPPER function is UPPER(c)

– Where c is the character string or field to be converted into uppercase characters


UPPER Function – manage user input

Figure 10-3 Using UPPER function to manage user input

-- chapter 10, Figure 10-3; p.335SELECT firstname, lastnameFROM customersWHERE lastname = UPPER('&Custval');


INITCAP Function• Used to convert character strings to mixed case,

which each word beginning with a capital letter.

Figure 10-4 INITCAP function in a SELECT clause modifies the display


Character Manipulation Functions

• Character manipulation functions manipulate data by extracting substrings, counting the number of characters, replacing strings, etc.


SUBSTR Function• Used to return a substring, or portion of a string

Figure 10-6 Comparison of SUBSTR arguments

SUBSTR (c, p, l)Where c: the character stringp: the beginning character position,l: the length of the string to return in the query result.-p: backward “p” position

-1-2-3


INSTR Function

Figure 10-7 Comparison of INSTR arguments

start_position := INSTR(original_string, substring, starting_pos, occurrence#);/* the first two arguments are required, the last two arguments are optional */

9 14

Why?

10

1059


Procedural programming Language Uses detailed instructions Processes statements sequentially

Combines SQL commands with procedural instructions

Used to perform sequential processing using an Oracle database

What is PL/SQL?


Why PL/SQL?

SQL

PL/SQL

GUIComponents

(reports, forms, graphics etc.)

D.B.

ORACLE(programming language

components)


Using SQL Commands in PL/SQL Programs

______COMMIT, ROLLBACK, SAVEPOINT

Organize DML commands into logical transactions

Transaction control commands

______SELECT, INSERT, UPDATE, DELETE

Query or change the data in the database tables

Data Manipulation Language (DML)

_____CREATE, ALTER, DROP, GRANT, REVOKE

Create/change the database structure

Date Definition Language (DDL)

Can Be Used in PL/SQL

Examples of Commands

PurposeCategory


Fundamentals of PL/SQL

• Full-featured programming language• Execute using Oracle 12c utilities

– SQL*Plus– Forms Builder

• An interpreted language• Semicolon ends each command• Reserved words• Type in editor, execute in SQL*Plus


Table: PL/SQL command capitalization styles

s_first_name, faculty_idLowercaseVariable names

student, fidLowercaseDatabase objects

SELECT, INSERTUppercaseSQL commands

VARCHAR2, NUMBERUppercasePredefined data types

COUNT, TO_DATEUppercaseBuilt-in functions

BEGIN, DECLAREUppercaseReserved Words

ExampleCapitalizationItem Type

Student_F_Name, Faculty_IDMixed case


Identifiers and Variables:Rules for Names and Properties

• From 1 to 30 characters• Only alphanumeric characters, and special

characters ($ _ #)• Must begin with a letter and can not contain

blank spaces or hyphens

And sure they cannot be reserved words (e.g., BEGIN)


Variables and Data Types

• Variables– Used to store numbers, character strings, dates,

and other data values– Avoid using keywords, table names and column

names as variable names– Must be declared with data type before use:

variable_name data_type_declaration;e.g., current_s_id NUMBER(6);


Language Elements:PL/SQL Data Types

• Scalar– References a single value

• Composite– References a data structure

• Reference– References a specific database item (e.g., %TYPE,

%ROWTYPE)• LOB

– References a large binary object (e.g., graphs, video)

(we will focus on this type)


Scalar Data Types

• Represent a single value– Database scalar data types:


Scalar Data Types (cont.)

• Represent a single value– Non-database scalar data types:


Tables: PL/SQL data types

c_address customer.customer_address%; TYPEcust_order_recordcust_order% ROWTYPE;

Assumes the data type of a database record (entire row)

%ROWTYPE

Assumes the data type of a database field

%TYPE

order_flag BOOLEAN;True/False valuesBOOLEAN

todays_date DATE;DatesDATE

evaluation_summary LONG;Text, up to 32,760 bytesLONG

current_price NUMBER(5,2);Floating, fixed-point, or integer number

NUMBER

student_gender CHAR(1);Fixed-length character strings

CHAR

student_name VARCHAR2(30);

Variable-length character strings

VARCHAR2

Sample DeclarationUsageData Type


Block Structure

PL/SQL is a “block structured” language.

That just means everything you do is done in terms of blocks of code.

All PL/SQL blocks share the same basic structure.

-- Figure 4-1; p.195

________ /”HEADER”

<variable declarations>;

________

<body executable code>;

EXCEPTION

<exception/error handling code>;

_______;

Comments: Not executed by interpreter Enclosed between /* and */ On one line beginning with --


Comment Statements

There are two types of comments in PL/SQL: Single-line and multi-line.Single Line:

x := 4; -- assign 4 to the variable xMulti-line:

/* Assign 4 to

the variable x */

x := 4;


Assignment Statements

• Assigns a value to a variablevariable_name := value;

• Value can be a literal:current_s_first_name := 'John';

• Value can be another variable:current_s_first_name := s_first_name;


Executing a PL/SQL Program in SQL*Plus

• Create program in text editor (using Notepad)

• Paste into SQL*Plus window

• Press Enter, type / then enter to execute

• SET SERVEROUTPUT ON SIZE 4000

• SET SERVEROUTPUT ON

-- PL/SQL #1: *** with syntax error ***DECLARE todays_date DATE;BEGIN todays_date = SYSDATE; DBMS_OUTPUT.PUT_LINE('Today''s date is '); DBMS_OUTPUT.PUT_LINE(todays_date);END;-- PL/SQL #2DECLARE todays_date DATE;BEGIN todays_date := SYSDATE; DBMS_OUTPUT.PUT_LINE('Today’’s date is '); DBMS_OUTPUT.PUT_LINE(todays_date);END;


-- PL/SQL #3a (ok for this version)--PL/SQL program to display the current dateDECLARE todays_date DATE;BEGIN todays_date := SYSDATE; DBMS_OUTPUT.PUT_LINE('Today''s date is ' || (todays_date));END;

--PL/SQL#3b program to display the current date-- CURRENT_DATE returns the current date and time from the user session (from -- client software and it may be in a different location from the server database (p.355)DECLARE todays_date DATE;BEGIN todays_date := CURRENT_DATE; DBMS_OUTPUT.PUT_LINE('Today''s date is ' || TO_CHAR(todays_date));END;

What is the difference between these two outputs?How can we display all “Date” information (eg., NOVEMBER 12, 12:25:58 P.M. 2013)?


--PL/SQL#3C program to display the current date--see Table 10-4 (p.366) for more detailsDECLARE todays_date DATE;BEGIN todays_date := SYSDATE; DBMS_OUTPUT.PUT_LINE('Today''s date is ' || TO_CHAR(todays_date, 'MONTH DD, HH:MI:SS A.M. YYYY'));END;

Today's date is NOVEMBER 08, 09:25:58 A.M. 2016

--PL/SQL#3d program to display the current dateDECLARE todays_date DATE;BEGIN todays_date := SYSDATE; DBMS_OUTPUT.PUT_LINE('Today''s date is ' || TO_CHAR(todays_date, 'Day, MM-DD-YYYY, HH24:MI:SS'));END;

Today's date is Tuesday, 11-08-2016, 09:42:03


--PL/SQL#4 program to display the current dateDECLARE todays_date DATE; current_day VARCHAR2(9); current_day_length BINARY_INTEGER;BEGIN todays_date := SYSDATE; -- extract day portion from current date, and trim trailing blank spaces current_day := TO_CHAR(todays_date, 'DAY'); current_day := RTRIM(current_day); -- convert day to mixed case letters with initial letter capitalized current_day := INITCAP(current_day); -- determine length of day's character string current_day_length := LENGTH(current_day); DBMS_OUTPUT.PUT_LINE('Today''s date is ' || current_day || ', ' || TO_CHAR(todays_date)); DBMS_OUTPUT.PUT_LINE('The length of the word ' || current_day || ' is ' || TO_CHAR(current_day_length) || ' characters.');END;


Data Type Conversion Functions

Function Description Example

TO_DATE Converts a character string TO_DATE(‘07/14/06’,’MM/DD/YY’); to a date

TO_NUMBER Converts a character string TO_NUMBER(‘2’); to a number

TO_CHAR Converts either a number or TO_CHAR(2); a date to a character string TO_CHAR(SYSDATE);if today is: return ‘October’ TO_CHAR(SYSDATE, ‘MONTH’);Tuesday, return ‘Tuesday’ TO_CHAR(SYSDATE, ‘DAY’);October 15, return ‘15’ TO_CHAR(SYSDATE, ‘DD’);2016 return ‘11:30 AM’ TO_CHAR(curr_time, ‘HH:MI AM’);


Debugging PL/SQL Programs

• Syntax error:– Command does not follow the guidelines of the

programming language– Generates compiler or interpreter error

messages• Logic error:

– Program runs but results in an incorrect result– Caused by mistake in program

_____ ______ error


-- PL/SQL#5a Program with a logic error and debugging statementsDECLARE curr_call_id VARCHAR2(30) := 'MIS 101'; blank_space NUMBER(2); curr_dept VARCHAR2(30); curr_number VARCHAR2(30);BEGIN blank_space := INSTR(curr_call_id,' '); curr_dept := SUBSTR(curr_call_id, 1, (blank_space - 1)); DBMS_OUTPUT.PUT_LINE('Call ID department is: ' || curr_dept); DBMS_OUTPUT.PUT_LINE('Original string value: ' || curr_call_id); DBMS_OUTPUT.PUT_LINE('Start position: ' || blank_space); DBMS_OUTPUT.PUT_LINE('Number of characters: ' || (LENGTH(curr_call_id) - blank_space)); curr_number := SUBSTR(curr_call_id, blank_space, (LENGTH(curr_call_id) - blank_space)); DBMS_OUTPUT.PUT_LINE('Course Number is: ' || curr_number);END;

Call ID department is: MISOriginal string value: MIS 101Start position: 4Number of characters: 3Course Number is: 10

PL/SQL procedure successfully completed.


-- PL/SQL#5b Program with a correct logicDECLARE curr_call_id VARCHAR2(30) := 'MIS 101'; blank_space NUMBER(2); curr_dept VARCHAR2(30); curr_number VARCHAR2(30);BEGIN blank_space := INSTR(curr_call_id,' '); curr_dept := SUBSTR(curr_call_id, 1, (blank_space - 1)); DBMS_OUTPUT.PUT_LINE('Call ID department is: ' || curr_dept); DBMS_OUTPUT.PUT_LINE('Original string value: ' || curr_call_id); DBMS_OUTPUT.PUT_LINE('Start position: ' || blank_space); DBMS_OUTPUT.PUT_LINE('Number of characters: ' || (LENGTH(curr_call_id) - blank_space)); curr_number := SUBSTR(curr_call_id, (blank_space+1), (LENGTH(curr_call_id) - blank_space)); DBMS_OUTPUT.PUT_LINE('Course Number is: ' || curr_number);END;

Call ID department is: MISOriginal string value: MIS 101Start position: 4Number of characters: 3Course Number is: 101

PL/SQL procedure successfully completed.


Other Functions

• NVL• NVL2


NVL and NVL2 (p.377)

1. Which function should be used to replace a NULL value with a numeric value for calculation purposes? ANSWER: _______

2. A NULL value can be replaced by a text message, while displaying a different message if there is not a NULL value, using which function? ANSWER: ______

NVL

NVL2

NVL(x,y): y represents the value to substitute if x is NULL. In many cases, the substitute for a NULL value ina calculation is zero (0)


-- chapter 10, Figure 10-33; p.378SELECT title, retail, discount, retail-discount "Sales price“ FROM books;

TITLE RETAIL DISCOUNT Sales price------------------------------ ---------- ---------- -----------BODYBUILD IN 10 MINUTES A DAY 30.95REVENGE OF MICKEY 22BUILDING A CAR WITH TOOTHPICKS 59.95 3 56.95DATABASE IMPLEMENTATION 55.95COOKING WITH MUSHROOMS 19.95HOLY GRAIL OF ORACLE 75.95 3.8 72.15HANDCRANKED COMPUTERS 25E-BUSINESS THE EASY WAY 54.5PAINLESS CHILD-REARING 89.95 4.5 85.45THE WOK WAY TO COOK 28.75BIG BEAR AND LITTLE DOVE 8.95HOW TO GET FASTER PIZZA 29.95 1.5 28.45HOW TO MANAGE THE MANAGER 31.95SHORTEST POEMS 39.95

14 rows selected.


-- chapter 10, Figure 10-34; p.361SELECT title, retail, discount, retail-NVL(discount, 0) "Sales price“ FROM books;

TITLE RETAIL DISCOUNT Sales price------------------------------ ---------- ---------- -----------BODYBUILD IN 10 MINUTES A DAY 30.95 30.95REVENGE OF MICKEY 22 22BUILDING A CAR WITH TOOTHPICKS 59.95 3 56.95DATABASE IMPLEMENTATION 55.95 55.95COOKING WITH MUSHROOMS 19.95 19.95HOLY GRAIL OF ORACLE 75.95 3.8 72.15HANDCRANKED COMPUTERS 25 25E-BUSINESS THE EASY WAY 54.5 54.5PAINLESS CHILD-REARING 89.95 4.5 85.45THE WOK WAY TO COOK 28.75 28.75BIG BEAR AND LITTLE DOVE 8.95 8.95HOW TO GET FASTER PIZZA 29.95 1.5 28.45HOW TO MANAGE THE MANAGER 31.95 31.95SHORTEST POEMS 39.95 39.95

14 rows selected.

What is the difference between these two versions?


-- chapter 10, Figure 10-35; p.380 (version b)SELECT order#, orderdate, shipdateFROM ordersWHERE orderdate >= '03-APR-09';

ORDER# ORDERDATE SHIPDATE---------- --------- --------- 1009 03-APR-09 05-APR-09 1010 03-APR-09 04-APR-09 1011 03-APR-09 05-APR-09 1012 03-APR-09 1013 03-APR-09 04-APR-09 1014 04-APR-09 05-APR-09 1015 04-APR-09 1016 04-APR-09 1017 04-APR-09 05-APR-09 1018 05-APR-09 1019 05-APR-09 1020 05-APR-09

12 rows selected.

NULL

NULL


-- chapter 10, Figure 10-35; p.380 (version c)SELECT order#, orderdate, shipdate, (shipdate - orderdate) "Ship Days"FROM ordersWHERE orderdate >= '03-APR-09';

ORDER# ORDERDATE SHIPDATE Ship Days---------- --------- --------- ---------- 1009 03-APR-09 05-APR-09 2 1010 03-APR-09 04-APR-09 1 1011 03-APR-09 05-APR-09 2 1012 03-APR-09 1013 03-APR-09 04-APR-09 1 1014 04-APR-09 05-APR-09 1 1015 04-APR-09 1016 04-APR-09 1017 04-APR-09 05-APR-09 1 1018 05-APR-09 1019 05-APR-09 1020 05-APR-09

12 rows selected.


-- chapter 10, Figure 10-35; p.380SELECT order#, orderdate, shipdate,NVL(shipdate, '06-APR-09') - orderdate "Ship Days"FROM ordersWHERE orderdate >= '03-APR-09';

ORDER# ORDERDATE SHIPDATE Ship Days---------- --------- --------- ---------- 1009 03-APR-09 05-APR-09 2 1010 03-APR-09 04-APR-09 1 1011 03-APR-09 05-APR-09 2 1012 03-APR-09 3 1013 03-APR-09 04-APR-09 1 1014 04-APR-09 05-APR-09 1 1015 04-APR-09 2 1016 04-APR-09 2 1017 04-APR-09 05-APR-09 1 1018 05-APR-09 1 1019 05-APR-09 1 1020 05-APR-09 1

12 rows selected.

Substitutes a value for a NULL value

NULL

If shipdate is NULL, substitutes with ’06-APR-09’


NVL Function• Substitutes a value for a NULL value

Figure 10-35 Date calculations involving a NULL value


-- chapter 10, Figure 10-35; p.380 (version b)SELECT order#, orderdate, shipdateFROM ordersWHERE orderdate >= '03-APR-09';

ORDER# ORDERDATE SHIPDATE---------- --------- --------- 1009 03-APR-09 05-APR-09 1010 03-APR-09 04-APR-09 1011 03-APR-09 05-APR-09 1012 03-APR-09 1013 03-APR-09 04-APR-09 1014 04-APR-09 05-APR-09 1015 04-APR-09 1016 04-APR-09 1017 04-APR-09 05-APR-09 1018 05-APR-09 1019 05-APR-09 1020 05-APR-09

12 rows selected.

NULL

NULL


-- chapter 10, Figure 10-36; p.381SELECT order#, orderdate,NVL2(shipdate, 'Shipped', 'Not Shipped') "Status"FROM ordersWHERE orderdate >= '03-APR-09';

ORDER# ORDERDATE Status---------- --------- ----------- 1009 03-APR-09 Shipped 1010 03-APR-09 Shipped 1011 03-APR-09 Shipped 1012 03-APR-09 Not Shipped 1013 03-APR-09 Shipped 1014 04-APR-09 Shipped 1015 04-APR-09 Not Shipped 1016 04-APR-09 Not Shipped 1017 04-APR-09 Shipped 1018 05-APR-09 Not Shipped 1019 05-APR-09 Not Shipped 1020 05-APR-09 Not Shipped

12 rows selected.

IF NULL

IF NOT NULL


NVL2 Function• Allows different actions based on whether a value is NULL

Figure 10-36 Using NVL2 to substitute values


Terminology

• Function – predefined block of code that accepts arguments

• Single-row function – returns one row of results for each record processed

• Multiple-row function – returns one result per group of data processed (covered in the next chapter)


Types of Functions

Table 10-1 Functions Covered in This Chapter


• Practice all the examples in the text.• A Script file is available on the Bb (file

name: Ch10Queries.sql)• After completing all examples, do the HW.


Homework - Hands-On Assignments

Read and Practice all examples on Chapters 10• 1. Run the script files (in the folder \oradata\

chapter10\): JLDB_Build_10.sql and download other data files

• 2. Read Oracle assignment and create a script file Oracle_ch10_Lname_Fname.sql for questions (#3,4,10; p.399) on “Hands-on Assignments”. Use appropriate COLUMN statements to produce readable outputs

• 3. Execute and test one problem at a time and make sure they are all running successfully.

• 4. When you done, spool the script files (see next slide for spooling instructions) and UPLOAD the file (Oracle_ch10_Spool_Lname_Fname.txt) to Bb by the midnight before the next class.

Upload the spooled file (*.txt) to the Bb (under “Assignments & Projects”) by the deadline.


How to Spool your Script and Output FilesAfter you tested the script file of Oracle_ch10_Lname_Fname.sql

successfully, follow the instructions below to spool both script and output files:

Step 0. Run the following script file from SQL*Plus (since you have created JLDB tables)– Start c:\oradata\chapter10\JLDB_Build_10.sql

• 1. type the following on SQL>– Spool c:\oradata\Oracle_ch10_Spool_Lname_Fname.txt (make sure your name is

entered)• 2. open Oracle_ch10_Lname_Fname.sql that you already tested• 3. copy and paste all the SQL commands (including all comments) to the

SQL*PLUS • 4. type Spool Off on the SQL>The output should contain your personal information, all SQL commands and

their solution on the .txt file and saved in C: drive (oradata\ folder)

Upload the spooled file (*.txt) to the Bb (under “Assignments & Projects”) by the deadline.


Your Turn …

• PART II– Study yourself– “Learning to learn and learning to change”


Nesting Functions

Figure 10-8 INSTR nested inside SUBSTR


LENGTH Function• Used to determine the number of characters in a string

Figure 10-10 Checking data width with the LENGTH function


LTRIM and RTRIM Functions

• Used to remove a specific string of characters

Figure 10-12 Using the LTRIM function


REPLACE Function

• Substitutes a string with another specified string

Figure 10-13 Using the REPLACE function


TRANSLATE Function

Figure 10-14 Using TRANSLATE to substitute character values


CONCAT Function

• Used to concatenate two character strings

Figure 10-15 Using the CONCAT function


Number Functions

• Allow for manipulation of numeric data– ROUND– TRUNC– MOD– ABS


ROUND Function• Used to round numeric columns to a stated precision

Figure 10-16 Using the ROUND function to round numbers to various places


TRUNC Function• Used to truncate a numeric value to a specific position

Figure 10-17 Using the TRUNC function to truncate numbers at various places


MOD Function

Figure 10-18 Using the MOD functions to return the remainder


ABS Function

Figure 10-19 The effect of using the ABS function


Date Functions

• Used to perform date calculations or format date values• Subtract date for number of days difference

Figure 10-20 A calculation with date columns


MONTHS_BETWEEN Function

• Determines the number of months between two dates

Figure 10-21 Using the MONTHS_BETWEEN function


ADD_MONTHS Function

• Adds a specified number of months to a date

Figure 10-22 Using the ADD_MONTHS function


NEXT_DAY Function

• Determines the next occurrence of a specified day of the week after a given date

Figure 10-23 Using the NEXT_DAY function


TO_DATE Function

• Converts various date formats to the internal format (DD-MON-YY) used by Oracle 11g

Figure 10-25 Using the TO_DATE function


Format Model Elements - Dates

Table 10-2 Format Arguments for Dates


ROUND Function

Figure 10-26 Rounding dates by month and year


TRUNC Function

Figure 10-27 Using the TRUNC function on date calculation results


TO_CHAR Function

• Converts dates and numbers to a formatted character string

Figure 10-39 Formatting values for display with TO_CHAR


TO_NUMBER Function

Figure 10-43 Using the TO_NUMBER function to convert a string to a numeric datatype


DUAL Table

• Dummy table• Consists of one column and one row• Can be used for table reference in the FROM

clause


Using DUAL

Figure 10-44 Practicing functions by using a DUAL table


Summary

• Single-row functions return a result for each row or record processed

• Case conversion functions such as UPPER, LOWER, and INITCAP can be used to alter the case of character strings

• Character manipulation functions can be used to extract substrings (portions of a string), identify the position of a substring in a string, replace occurrences of a string with another string, determine the length of a character string, and trim spaces or characters from strings

• Nesting one function within another allows multiple operations to be performed on data


Summary (continued)

• Simple number functions such as ROUND and TRUNC can round or truncate a number on both the left and right side of a decimal

• The MOD function is used to return the remainder of a division operation

• Date functions can be used to perform calculations with dates or to change the format of dates entered by a user

• Regular expressions enable complex pattern matching operations

• The NVL, NVL2, and NULLIF functions are used to address problems encountered with NULL values


Summary (continued)

• The TO_CHAR function lets a user present numeric data and dates in a specific format

• The DECODE function allows an action to be taken to be determined by a specific value

• The searched CASE expression enables you to evaluate conditions to determine the resulting value

• The SOUNDEX function looks for records based on the phonetic representation of characters

• The DUAL table can be helpful when testing functions

pl/sql and chapter 10 selected single-row functions

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