Chapter 3:
Table Creation and Management:
Creating and Modifying
Database Tables
Jason C. H. Chen, Ph.D.
Professor of MIS
School of Business Administration
Gonzaga University
Spokane, WA 99258
chen@jepson.gonzaga.edu
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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
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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
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Basic SQL Concepts and Commands
SQL (Structured Query Language) is used to
manipulate the database.
There are two basic types of SQL commands:
Data Definition Language (DDL)
Data Manipulation Language (DML)
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
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Security Granting Table Privileges
• Security is the prevention of unauthorized access
to the database. Within an organization, the
database administrator determines the types of
access various users need for the database.
• Some users might be able to retrieve and update
data in the database. Other users might be able to
retrieve any data from the database but not make
any changes to it. Still other users might be able
to access only a portion of the database.
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Oracle11g 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
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A. Names and Properties
Why need a name?
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Creating a Table
CREATE TABLE tablename
(fieldname1 data_type (size),
fieldname2 data_type (size),
…);
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Defining Oracle10g Database Tables
• To create a table, you must specify:
–
–
–
–
Table name
Field names
Field data types
Field sizes
Constraints
restrictions on the data values that a field can store
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I. Names and Properties: Conventions
Series of rules Oracle Corporation established for
naming all database objects
1. From 1 to 30 characters
2. Only alphanumeric characters, and special
characters ($ , _, #)
3. Must begin with a letter and can not contain blank
spaces or hyphens
4. Must be unique and No reserved words are allowed
Are the following names (for field) valid? Why?
customer order
customer-order
#order
Customer_#
Customer#
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Oracle 11g 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
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II. Data Types
• Built-in
– provided by the system
• Library
– built by the software
vendor or a third party
• User-defined
– built by users
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Basic Built-In Data Types
•
Character
– VARCHAR2
– CHAR
• Numeric
•
•
– NUMBER
DATE
OTHERS:
– LOB, BLOB, LONG, RAW, LONG RAW
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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’
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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
[optional]
– 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;
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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.’
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Question: Which query will possibly generate
student information?
s_Last VARCHAR2(15);
s_Last CHAR(15);
SELECT s_Last, s_First,
s_Address
FROM student
WHERE s_Last = ‘Smith’;
SELECT s_Last, s_First,
s_Address
FROM student
WHERE s_Last = ‘Smith’;
• What data type should be used if there is any
chance that all column spaces will NOT be filled?
VARCHAR2
• Answer: ______________
L
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• 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.
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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
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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
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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:
–
–
–
Dr. Chen, Oracle Database System (Oracle)
TO_DATE (‘
TO_DATE (‘
TO_DATE (‘
’, ‘MM/DD/YY’)
‘, ‘DD-MON-YYYY’)
‘, ‘HH:MI AM’)
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Table Design (continued)
Table 3-2
Oracle 11g Datatypes
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Table Creation
Figure 3-1
CREATE TABLE syntax
Defining Columns
• Column definition list must be enclosed in
parentheses
• Datatype must be specified for each column
• Maximum of 1,000 columns
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Exercise: Create a new table of “acctmanager” based on
the following information
acctmanager
Amid
Amfirst
Amlast
AmeDate
Amsal
Amcomm
Region
VARCHAR2(4)
VARCHAR2(12)
VARCHAR2(12)
DATE
NUMBER(8,2)
NUMBER(7,2)
CHAR(2)
CREATE TABLE acctmanager
( amid
…
Dr. Chen, Oracle Database System (Oracle)
NOT NULL);
GROUP WORK
Complete the
CREATE command
manually!
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Exercise: Create a new table of “acctmanager” based on
the following information
acctmanager
Amid
Amfirst
Amlast
AmeDate
Amsal
Amcomm
Region
VARCHAR2(4)
VARCHAR2(12)
VARCHAR2(12)
DATE
NUMBER(8,2)
NUMBER(7,2)
CHAR(2)
CREATE TABLE acctmanager
( amid VARCHAR2(4) PRIMARY KEY,
SELECT *
amfirst VARCHAR2(12) NOT NULL,
FROM acctmanager;
amlast VARCHAR2(12) NOT NULL,
amedate DATE DEFAULT SYSDATE,
amsal NUMBER(8,2),
amcomm NUMBER(7,2) DEFAULT 0,
region CHAR(2) NOT NULL);
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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
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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
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CREATE TABLE Command Example
What is the difference
between these two versions:
Virtual Column/
(Derived/computed)
Is this a good approach?
Figure 3-2
The creation of the ACCTMANAGER table
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Viewing Table Structures: DESCRIBE
• DESCRIBE displays the structure of a specified table
Figure 3-4
The DESCRIBE command
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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 3-8
CREATE TABLE … AS command syntax
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CREATE TABLE…AS Command Example
(You need to apply this to #7 on p.94)
Figure 3-7
Creating a table based on a subquery
SELECT * FROM cust_mkt;
DESC cust_mkt;
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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 3-10 Arithmetic operations with NULL values
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ALTER TABLE…ADD Command
Figure 3-12 The ALTER TABLE … ADD command
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ALTER TABLE…MODIFY Command
Figure 3-18 The ALTER TABLE … MODIFY command to increase the column width
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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
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ALTER TABLE…SET UNUSED Command
• Once marked for deletion, a column cannot be
restored
• Storage space is freed at a later time
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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?
ALTER TABLE author
DROP UNUSED COLUMNS;
Dr. Chen, Oracle Database System (Oracle)
Show: test_UNUSED.sql
and test_UNUSED.docx
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AUTHOR
AuthorID
LName
VARCHAR2(4) VARCHAR2(10)
FName
VARCHAR2(10)
SQL> SELECT * FROM author;
AUTH
---S100
J100
A100
M100
K100
P100
A105
B100
P105
W100
W105
LNAME
---------SMITH
JONES
AUSTIN
MARTINEZ
KZOCHSKY
PORTER
ADAMS
BAKER
PETERSON
WHITE
WHITE
FNAME
---------SAM
JANICE
JAMES
SHEILA
TAMARA
LISA
JUAN
JACK
TINA
WILLIAM
LISA
AUTH
---R100
F100
W110
LNAME
---------ROBINSON
FIELDS
WILKINSON
FNAME
---------ROBERT
OSCAR
ANTHONY
14 rows selected.
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AUTHOR
AuthorID
LName
VARCHAR2(4) VARCHAR2(10)
FName
VARCHAR2(10)
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>
Dr. Chen, Oracle Database System (Oracle)
Show: test_UNUSED.sql
and test_UNUSED.doc
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>
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AUTHOR
AuthorID
LName
VARCHAR2(4) VARCHAR2(10)
FName
VARCHAR2(10)
SQL> SELECT * FROM author;
AUTH
---A100
A105
B100
F100
J100
K100
M100
P100
P105
R100
S100
AUTH
---W100
W105
W110
14 rows selected.
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• 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.
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Homework - Hands-On Assignments
Email me with one attachment
(Oracle_ch3_Spool_Lname_Fname.) to:
chen@jepson.gonzaga.edu
with subject title of
Bmis441-01_Oracle_ch3 (or Bmis441-02_Oracle_ch3)
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.94) 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 email the file
(Oracle_ch3_Spool_Lname_Fname.txt) to me by the
midnight before the next class. Turn in a hardcopy to me
in the class.
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How to Spool your Script and Output Files
After 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)
Email me with the spooled file (.txt) with attachment to:
chen@jepson.gonzaga.edu
with subject title of
Bmis441-01_Oracle_ch3 (or Bmis441-02_Oracle_ch3)
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• End of chapter 3
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