chapter 3: table creation and management: creating and modifying database tables

Dr. Chen, Oracle Database System (Oracle) 1

Chapter 3: Table Creation and Management:

Creating and ModifyingDatabase Tables

Jason C. H. Chen, Ph.D.Professor of MIS

School of Business AdministrationGonzaga UniversitySpokane, WA [email protected]


Important/Useful Links for SQL1. Below are three links of free “online interactive SQL Tutorial for Data Analysis and Query Examples” https://community.modeanalytics.com/sql/tutorial/introduction-to-sql/https://www.pgexercises.com/questions/basic/https://sqlbolt.com/

2. Furthermore, the link below is a fun read about the history of SQL, and growth of SQL:

https://blog.timescale.com/why-sql-beating-nosql-what-this-means-for-future-of-data-time-series-database-348b777b847a

https://community.modeanalytics.com/sql/tutorial/introduction-to-sql/




https://www.pgexercises.com/questions/basic/



https://sqlbolt.com/







Objectives

• Become acquainted with Structured Query Language (SQL)

• Identify the table name and structure• Create a new table using the CREATE TABLE command• Use a subquery to create a new table• Add a column to an existing table• Modify the definition of a column in an existing table• Delete a column from an existing table• Mark a column as unused and then delete it at a later time• Rename a table• Truncate a table• Drop a table


Database Objects and Queries

• An Oracle database consists of multiple user accounts• Each user account owns database objects

– Tables– Views– Stored programs, etc.

• Query: command to perform operation on database object

• Structured Query Language (SQL)– Industry standard query language for most of relational

databases– Consists of about 30 commands


Basic SQL Concepts and CommandsSQL (Structured Query Language) is used to manipulate the database.

There are two basic types of SQL commands:

DDL commands work with the structure of the objects (tables, indexes, views) in the database.

DML commands work with the data in the database (i.e.,manipulate the data). Reserved words - SQL command words

4Data Definition Language (DDL)

4Data Manipulation Language (DML)


Oracle12c User Accounts

• User account - identified by a unique username and password

• User schema - all of the objects that the user creates and stores in the database

• Database objects– Also called schema objects– Objects in user schema

• Object owner has privileges to perform all possible actions on an object

• Schema is a collection of objects in a specific Oracle account (tables, views etc.)


A. Names and PropertiesWhy need a name?


Creating a Table

CREATE TABLE tablename(fieldname1 data_type (size), fieldname2 data_type (size),

…);


Defining Oracle12c Database Tables

• To create a table, you must specify:– Table name– Field names– Field data types– Field sizes

vConstraintsrestrictions on the data values that a field can store


I. Names and Properties: Conventions

1. From 1 to 30 characters2. Only alphanumeric characters, and special

characters ($ , _, #)3. Must begin with a letter and can not contain blank

spaces or hyphens4. Must be unique and No reserved words are allowed

Series of rules Oracle Corporation established for naming all database objects

v Are the following names (for field) valid? Why? customer order customer-order

#orderCustomer_#Customer#


Oracle 12c Data Types

• Data type – Specifies kind of data that column stores– Provides means for error checking– Enable DBMS to use storage space more

efficiently by internally storing different types of data in different ways

– Basic types• Character• Number• Date/time


II. Data Types

• Built-in – provided by the system

• Library– built by the software

vendor or a third party• User-defined

– built by users


Basic Built-In Data Types

• Character– VARCHAR2– CHAR

• Numeric – NUMBER

• DATE• OTHERS:

– LOB, BLOB, LONG, RAW, LONG RAW


Character Data Types

• 1. VARCHAR2 –Stores variable-length character data up

to a maximum of 4,000 characters–Values in different records can have a

different number of characters– fieldname VARCHAR2(maximum_size)

• (e.g.) emp_name VARCHAR2(20);• an instance: ‘Jason Chen’


Character Data Types (cont.)

• 2. CHAR– Fixed-length character data (<= 2000 characters)– default is 1 if no field size is specified– Data values for different records all have the same number

of characters– DBMS adds trailing blank spaces to the end of the entry to

make the entry fill the maximum_size value– Data longer than maximum_size causes an error– fieldname CHAR[(maximum_size)]

• pros: use data storage space more efficiently and processed faster

• cons: causes inconsistent query results in other Oracle applications

– e.g. s_class CHAR(2); ‘SR’ ‘JR’ ‘SO’ ‘FR’ ‘GR’

– State CHAR(2) DEFAULT ‘WA’;– student_gender CHAR;

[optional]


Character Subtypes

Examples:VARCHAR2(5) ‘Smith’ or ‘Smi’CHAR(5) ‘Smith’ or ‘Smi ’LONG ‘Smith...’Note that you do not need to specify a size for LONG.To include a single quote in a literal character string, use two in a row:

‘This is Herald’’s string.’


Question: Which query will possibly generate student information?

• What data type should be used if there is any chance that all column spaces will NOT be filled?

• Answer: ______________

s_Last VARCHAR2(15);

SELECT s_Last, s_First, s_AddressFROM studentWHERE s_Last = ‘Smith’;

s_Last CHAR(15);

SELECT s_Last, s_First, s_AddressFROM studentWHERE s_Last = ‘Smith’;

L

VARCHAR2


• When use Query: SELECT s_last, s_first, ssn, telephone

FROM student WHERE s_last = ‘Smith’; • Case is sensitive within the single

quotation.• SQL Plus commands are NOT case

sensitive, but Query within the single quotation are case sensitive.


3. Number Data Types

• Stores negative, positive, fixed, and floating point numbers between

10 -130 <= <=10 +126 precision up to 38 decimal places• General Syntax: fieldname NUMBER [([precision,] [scale])]• Integer: fieldname NUMBER(precision) • Fixed point: fieldname NUMBER[([precision],

[scale])] • Floating point: fieldname NUMBER


Number Data Types (examples)• a) Integer: Number (n)

– e.g. s_id NUMBER(5) • 12345

• b) Fixed-point numbers– e.g. current_price NUMBER (5, 2);

• 259.99 33.89• c) Fixed-point numbers (cont.)

– e.g. total_mileage NUMBER (5, 1); • 259.9 33.8

• d) Floating-point Number – with a variable number of decimal places– e.g. s_gpa NUMBER;

• 3.89 2.7569 3.2


4. Date and Time Data Types

• Date, time data subtypes– Store actual date and time values– DATE

• Dates from December 31, 4712 BC to December 31, 4712 AD– Default format DD-MON-YY– Default time format HH:MI:SS A.M.– fieldname DATE – Sample declaration:

• OrderDate DATE NOT NULL;– Use one of the following format masks:

– TO_DATE (‘ ’, ‘MM/DD/YY’) – TO_DATE (‘ ‘, ‘DD-MON-YYYY’) – TO_DATE (‘ ‘, ‘HH:MI AM’)


Table Design (continued)

Table 3-2 Oracle 11g Datatypes


Table Creation

• Column definition list must be enclosed in parentheses

• Datatype must be specified for each column• Maximum of 1,000 columns

Defining Columns

Figure 3-1 CREATE TABLE syntax


Refresh the Database

• 1. Create a new folder on c:\ as follows:c:\oradata\chapter3

• 2. Go to Blackboard and download data files from Oracle chapter3 and save under c:\oradata\chapter3\

• 3. Run the following script file– Start c:\oradata\chapter3\JLDB_Build_3.sql


Exercise – Your Turn• Type the following commands:

1) SELECT TABLE_NAME FROM USER_TABLES;

2) DROP TABLE ACCTMANAGER CASCADE CONSTRAINTS;

3) DROP TABLE ACCTMANAGER2 CASCADE CONSTRAINTS;

4) SELECT TABLE_NAME FROM USER_TABLES;

You now are able to create acctmanager table


acctmanager

Exercise: Create a new table of “acctmanager” based on the following information

CREATE TABLE (

… NOT NULL);

Amid Amfirst Amlast AmeDate Amsal Amcomm Region

VARCHAR2(4) VARCHAR2(12) VARCHAR2(12) DATE NUMBER(8,2) NUMBER(7,2) CHAR(2)

Exercise

Complete the CREATE command

manually!(call one student…)

acctmanageramid


acctmanager

Exercise: Create a new table of “acctmanager” based on the following information

CREATE TABLE ( amfirst VARCHAR2(12) NOT NULL,amlast VARCHAR2(12) NOT NULL,amedate DATE DEFAULT SYSDATE,amsal NUMBER(8,2),amcomm NUMBER(7,2) DEFAULT 0,region CHAR(2) NOT NULL);

Amid Amfirst Amlast AmeDate Amsal Amcomm Region

VARCHAR2(4) VARCHAR2(12) VARCHAR2(12) DATE NUMBER(8,2) NUMBER(7,2) CHAR(2)

How to verify the table structure of acctmanager?

DESC acctmanager;

acctmanageramid VARCHAR2(4) PRIMARY KEY,


CREATE TABLE Command Example

Virtual Column/(Derived/computed)

Figure 3-2 The creation of the ACCTMANAGER table

What is the difference between these two versions:

Is this a good approach?

When a value of amsal or amcomm is changed, its ameran will be updated automatically.


Viewing Table Structures: DESCRIBE

• DESCRIBE displays the structure of a specified table

Figure 3-4 The DESCRIBE command


Invisible Columns (p.68)

• Invisible columns are a new option in Oracle 12c. We can now create a column to make it hidden so it is not visible in basic statement such as a “SELECT” query.

• A developer may wish to make invisible columns if they need to reference a value in application logic but do not intend these values to be directly visible to users.

• Including the “invisible” option on a column definition as shown in Fig. 3-6 will establish an invisible column.


-- chapter 3, Figure 3-5; p. 68SELECT column_name, data_type, data_defaultFROM user_tab_columnsWHERE table_name = 'ACCTMANAGER';

-- chapter 3, Figure 3-6; p. 68CREATE TABLE TEST_INVIS(col1 CHAR(1),col2 NUMBER(4) invisible);

Fig 3-5 Verify DEFAULT and virtual column settings

-- chapter 3, Figure 3-7; p. 69SELECT *FROM test_invis;

-- chapter 3, Figure 3-8; p. 69SELECT col1, col2FROM test_invis;

-- chapter 3, Figure 3-9; P. 69SELECT column_name, hidden_columnFROM user_tab_colsWHERE table_name = ’TEST_INVIS’;


Table Creation through Subqueries

• You can use subqueries to retrieve data from an existing table

• Requires use of AS keyword• New column names can be assigned

CREATE TABLE…AS

Figure 3-10 CREATE TABLE … AS command syntax


CREATE TABLE…AS Command Example (You need to apply this to #7 on p.97)

Figure 3-11 Creating a table based on a subquery

SELECT * FROM cust_mkt;DESC cust_mkt;


Modifying Existing Tables• Accomplished through the ALTER TABLE

command• Use an ADD clause to add a column• Use a MODIFY clause to change a column• Use a DROP COLUMN to drop a column

– both “column” and its “data values” are deleted

ALTER TABLE Command Syntax

Figure 3-14 Arithmetic operations with NULL values


ALTER TABLE…ADD Command

Figure 3-16 The ALTER TABLE … ADD command


ALTER TABLE…MODIFY Command

Figure 3-22 The ALTER TABLE … MODIFY command to increase the column width


Modification Guidelines

• Column must be as wide as the data it already contains

• If a NUMBER column already contains data, size cannot be decreased

• Adding or changing default data does not affect existing data


ALTER TABLE…SET UNUSED Command

• Once marked for deletion (i.e., SET UNUSED), a column cannot be restored

• Storage space is freed at a later time

39


ALTER TABLE…DROP UNUSED Command

• Frees up storage space from columns previously marked as unused

However, once a table is set “UNUSED” it can’t be DROPPED using the following (regular) command:ALTER TABLE tablename DROP COLUMN colname; Then, what command can drop the “UNUSED” columns?

Show: test_UNUSED.sqland test_UNUSED.docx

ALTER TABLE authorDROP UNUSED COLUMNS;


AuthorID LName FNameVARCHAR2(4) VARCHAR2(10) VARCHAR2(10)

AUTHOR

SQL> SELECT * FROM author; AUTH LNAME FNAME ---- ---------- ---------- S100 SMITH SAM J100 JONES JANICE A100 AUSTIN JAMES M100 MARTINEZ SHEILA K100 KZOCHSKY TAMARA P100 PORTER LISA A105 ADAMS JUAN B100 BAKER JACK P105 PETERSON TINA W100 WHITE WILLIAM W105 WHITE LISA AUTH LNAME FNAME ---- ---------- ---------- R100 ROBINSON ROBERT F100 FIELDS OSCAR W110 WILKINSON ANTHONY 14 rows selected.



AUTHOR

SQL> describe author; Name Null? Type ------------ -------- --------------- AUTHORID NOT NULL VARCHAR2(4) LNAME VARCHAR2(10) FNAME VARCHAR2(10) SQL> SQL> ALTER TABLE author SET UNUSED COLUMN fname;Table altered.

SQL> describe author; Name Null? Type ----------- -------- ------------- AUTHORID NOT NULL VARCHAR2(4) LNAME VARCHAR2(10)SQL>

SQL> ALTER TABLE author DROP COLUMN lname; Table altered.

SQL> ALTER TABLE author DROP COLUMN fname;

ALTER TABLE author DROP COLUMN fname *ERROR at line 1:ORA-00904: "FNAME": invalid identifier

SQL> ALTER TABLE author 2 DROP UNUSED COLUMNS;

Table altered.

SQL> describe author; Name Null? Type ----------- -------- ------------- AUTHORID NOT NULL VARCHAR2(4)SQL>

Show: test_UNUSED.sqland test_UNUSED.docx


"is there any way that we can retrieve the data from the UNUSED column ?“

No. The SET UNUSED syntax is a convenience for DBAs. Dropping a column is potentially a resource-intensive exercise. Marking it as UNUSED is a lot quicker, so it allows them to withdraw a column from use in busy times and run DROP UNUSED when the database is quieter. But the data is as lost as if they had just dropped the column.

The only way to retrieve the data would be to restore the column, through one of the various Flashback features (depending on what you've got configured) or else RMAN (or whichever Backup/Recovery solution you have in place).



AUTHOR

SQL> SELECT * FROM author; AUTH----A100A105B100F100J100K100M100P100P105R100S100 AUTH----W100W105W110 14 rows selected.


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

name: Ch3Queries.sql)• After completing all examples, do the HW.


Homework - Hands-On Assignments

Read and Practice all examples on Chapters 3• 1. Run the script files (in the folder \oradata\chapter3\):

JLDB_Build_3.sql• 2. Read Oracle assignment and create a script file

Oracle_ch3_Lname_Fname.sql for questions (#1 to #8; p.97) on “Hands-on Assignments”. .

• 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 SQL and the spooled files (Oracle_ch3_Spool_Lname_Fname.txt) to Bb before next class begins. Turn in a hardcopy of spooled file (*.txt ONLY) to me in the class.

Upload the SQL and spooled files (*.sql and *.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_ch3_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\chapter3J\LDB_Build_3.sql

• 1. type the following on SQL>– Spool c:\oradata\Oracle_ch3_Spool_Lname_Fname.txt (make sure your name is entered)

• 2. open Oracle_ch3_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 SQL and spooled files (*.sql and *.txt) to the Bb (under “Assignments & Projects”) by the deadline


TRUNCATING a TABLE


Renaming a Table

• RENAME…TO is used to rename a table – the old name is no longer valid

Figure 3-32 The RENAME … TO command

--chapter 3, Figure 3-34; p.84

SELECT *FROM cust_mkt_092009;


Truncating a Table

• TRUNCATE TABLE command – rows are deleted

• Structure of table remains

Figure 3-36 The TRUNCATE TABLE command


Deleting a Table

• DROP TABLE command – table structure and contents are deleted

51

Figure 3-36 Deleting a Table command

--chapter 3, Figure 3-39; p. 87

DESC cust_mkt_092009


DROP TABLE without Purge Option

• Starting with Oracle 10g, a new feature of recycle bin was introduced.

• Dropped tables can be recovered from the recycle bin

Figure 3-40 Checking the recycle bin


FLASHBACK Command

• The FLASHBACK command recovers a table from the recycle bin

53

Figure 3-41 Using FLASHBACK TABLE to restore a dropped table


Use PURGE to Remove a Table from the Recycle Bin

Figure 3-40 Removing a table from the recycle bin


PURGE Option Available for DROP TABLE Command

• Using the PURGE option will permanently remove a table from the database

• The table will not be copied into the recycle bin

55

--chapter 3, Figure 3-44; p. 90

DROP TABLE cust_mkt_092009 PURGE;


• End of chapter 3

chapter 3: table creation and management: creating and modifying database tables

Documents

oracle database system

queriesan oracle database

database database objectsalso

database objectsare

specific oracle account

oracle10g database tablesto

kind of data

fieldname2 data