DDL(Data defination Language ) Using Oracle

Naming Rules
• Table names and column names:
– Must begin with a letter
– Must be 1–30 characters long
– Must contain only A–Z, a–z, 0–9, _, $, and #
– Must not duplicate the name of another object
owned by the same user
– Must not be an Oracle server reserved word

Data Types
Data Type Description
VARCHAR2(size) Variable-length character data
CHAR(size) Fixed-length character data
NUMBER(p,s) Variable-length numeric data
DATE Date and time values

Creating Tables
– Create the table.
– Confirm table creation.
DESCRIBE dept
CREATE TABLE dept
(deptno NUMBER(2),
dname VARCHAR2(14),
loc VARCHAR2(13),
create_date DATE DEFAULT SYSDATE);
Table created.

Constraints
– Create a constraint at either of the following times:
• At the same time as the table is created
• After the table has been created
– Define a constraint at the column or table level.
– View a constraint in the data dictionary.
• NOT NULL
• UNIQUE
• PRIMARY KEY
• FOREIGN KEY

Constraints...
– Column-level constraint:
– Table-level constraint:
column [CONSTRAINT constraint_name] constraint_type,
column,...
[CONSTRAINT constraint_name] constraint_type
(column, ...),

Defining Constraints
– Column-level constraint:
– Table-level constraint:
CREATE TABLE employees(
employee_id NUMBER(6)
CONSTRAINT emp_emp_id_pk PRIMARY KEY,
first_name VARCHAR2(20),
...);
employee_id NUMBER(6),
first_name VARCHAR2(20),
...
job_id VARCHAR2(10) NOT NULL,
CONSTRAINT emp_emp_id_pk
PRIMARY KEY (EMPLOYEE_ID));
1
2

The NOT NULL Constraint
• The NOT NULL constraint ensures that the column
has a value and the value is not a null value
• A space or a numeric zero is not a null value
• At the column level ONLY, the constraint is defined
by:
Name VARCHAR2(15) CONSTRAINT faculty_name_nn NOT NULL,

UNIQUE Constraint
• Defined at either the table level or the column
level:CREATE TABLE employees(
last_name VARCHAR2(25) NOT NULL,
email VARCHAR2(25),
salary NUMBER(8,2),
commission_pct NUMBER(2,2),
hire_date DATE NOT NULL,
...
CONSTRAINT emp_email_uk UNIQUE(email));

FOREIGN KEY Constraint
DEPARTMENTS
EMPLOYEES
FOREIGN
KEY
INSERT INTO
Not allowed
(9 does not
exist)
Allowed
PRIMARY
KEY
…
…

FOREIGN KEY Constraint
• Defined at table level only:
last_name VARCHAR2(25) NOT NULL,
email VARCHAR2(25),
salary NUMBER(8,2),
commission_pct NUMBER(2,2),
hire_date DATE NOT NULL,
...
department_id NUMBER(4),
CONSTRAINT emp_dept_fk FOREIGN KEY (department_id)
REFERENCES departments(department_id),
CONSTRAINT emp_email_uk UNIQUE(email));

FOREIGN KEY Constraint:
Keywords
– FOREIGN KEY: Defines the column in the child
table at the table-constraint level
– REFERENCES: Identifies the table and column in
the parent table

CHECK Constraint
– Defines a condition that each row must
satisfy
..., salary NUMBER(2)
CONSTRAINT emp_salary_min
CHECK (salary > 0),...

CREATE TABLE: Example
CREATE TABLE employees
( employee_id NUMBER(6)
CONSTRAINT emp_employee_id PRIMARY KEY
, first_name VARCHAR2(20)
, last_name VARCHAR2(25)
CONSTRAINT emp_last_name_nn NOT NULL
, email VARCHAR2(25)
CONSTRAINT emp_email_nn NOT NULL
CONSTRAINT emp_email_uk UNIQUE
, phone_number VARCHAR2(20)
, hire_date DATE
CONSTRAINT emp_hire_date_nn NOT NULL
, job_id VARCHAR2(10)
CONSTRAINT emp_job_nn NOT NULL
, salary NUMBER(8,2)
CONSTRAINT emp_salary_ck CHECK (salary>0)
, commission_pct NUMBER(2,2)
, manager_id NUMBER(6)
, department_id NUMBER(4)
CONSTRAINT emp_dept_fk REFERENCES
departments (department_id));

UPDATE employees
*
ERROR at line 1:
ORA-02291: integrity constraint (HR.EMP_DEPT_FK)
violated - parent key not found
UPDATE employees
SET department_id = 55
WHERE department_id = 110;
Violating Constraints

Violating Constraints
• You cannot delete a row that contains a
primary key that is used as a foreign key in
another table.DELETE FROM departments
DELETE FROM departments
*
ERROR at line 1:
ORA-02292: integrity constraint (HR.EMP_DEPT_FK)
violated - child record found

Creating a Table
by Using a Subquery
– Create a table and insert rows by combining the
CREATE TABLE statement and the AS
subquery option.
– Match the number of specified columns to the
number of subquery columns.
– Define columns with column names and
default values.
CREATE TABLE table
[(column, column...)]
AS subquery;

CREATE TABLE dept80
AS
SELECT employee_id, last_name,
salary*12 ANNSAL,
hire_date
FROM employees
Table created.
Creating a Table
by Using a Subquery
DESCRIBE dept80

ALTER TABLE Statement
• Use the ALTER TABLE statement to:
– Add a new column
– Modify an existing column
– Define a default value for the new column
– Drop a column
– Drop Constraint

Adding a New Column to an
Existing Table
• The general syntax to add a column to an
existing table is
ALTER TABLE tablename
ADD columnname datatype;
SQL> ALTER TABLE student
2 ADD SocialSecurity CHAR(9);
Table altered.
SQL>

Modifying an Existing Column
• The general syntax to modify an existing column is
MODIFY columnname newdatatype;
where newdatatype is the new data type or the new size for the
column.
SQL> ALTER TABLE student
2 MODIFY SocialSecurity VARCHAR2(11);
Table altered.
SQL>

Adding a Constraint
• To add a constraint using ALTER TABLE, the syntax for table
level constraint is used. The general syntax of ALTER TABLE is
ADD [CONSTRAINT constraint_name] constraint_type
(column, …),
SQL> ALTER TABLE COURSE
2 ADD CONSTRAINT COURSE_PREREQ_FK FOREIGN KEY (PREREQ)
3 REFERENCES COURSE(COURSEID);
Table altered.
SQL>

Dropping a Column and constrain
The general syntax is
• ALTER TABLE tablename DROP COLUMN columnname;
• ALTER TABLE tablename DROP CONSTRAINT constraintname;

Renaming a Table
– Additional DDL statements include the RENAME
statement, which is used to rename a table, view,
sequence.
– Syntax
– RENAME old_name TO new_name;
– In the syntax:
– old_name is the old name of the
table, view, sequence.
– new_name is the new name of the
table, view, sequence.

Views
• Provide security
• Create view viewName as select * from
tablename

• Create view.
• View can be insert/updated/deleted to reflect
changes in base table only if all not null
columns included in table and also view is
created by a single table.

More SQL Data Definition
Sequences
• Often we want to assign
each row a unique number
– These are useful as primary
keys
• In most versions of SQL we
can use autoincrementing
fields to do this
– Usually the first entry is
assigned 1, the next 2, and so
on, but Oracle lets you
change this

Sequences
• In Oracle we use a Sequence
– A sequence is a source of numbers
– We can declare several sequences, giving each a
name, a start point, and a step size
– We can then generate unique numbers by asking
for the next element from a sequence

Sequences in Oracle
• To declare a sequence:
CREATE SEQUENCE <name>
[START WITH <value>]
[INCREMENT BY <value>]
– If no START WITH or INCREMENT BY values
are given they default to 1
• To get the next value from a sequence
<sequence name>.nextVal

Sequence Example
• Creating a sequence
CREATE SEQUENCE mySeq START WITH 1
• Using a sequence
SELECT mySeq.nextVal FROM DUAL;
INSERT INTO Student
(stuID, stuName, stuAddress)
VALUES
(mySeq.nextVal, 'Steve Mills',
'13 Elm Street')

Oracle Data Dictionary
• To find the details of a table use
DESCRIBE <table name>
• Example:
SQL> DESCRIBE Student;
Name Null? Type
------------ -------- ----------
STUID NOT NULL NUMBER(38)
STUNAME NOT NULL VARCHAR2(50)
STUADDRESS VARCHAR2(50)
STUYEAR NUMBER(38)

Create synonym
• create synonyms so that other schemas can
access the new database objects (ie: tables)
without having to prefix the object names
• SELECT * FROM new_schema.suppliers;
• If you then created a synonym for
the suppliers table as follows:
• CREATE PUBLIC SYNONYM suppliers FOR
new_schema.suppliers;You could run the SELECT
statement as follows:
• SELECT * FROM suppliers;th the schema name.

33
DCL: Data Control Language
• Controlling Access to database objects such as tables
and views
• Example : Granting “Mary” the access to Table “student” (for inserting,
updating and deleting)
– GRANT INSERT, UPDATE, DELETE ON Emp TO Mary
– GRANT <privileges> ON <object name>
TO <grantee> [ <comma> <grantee> ... ]
[ WITH GRANT OPTION ]
– WITH GRANT OPTION: allows the grantee to further grant privileges
– Can be limited to a column of a table, Ex: GRANT UPDATE(name) ON emp TO
Mary
– To revoke privileges : REVOKE

• Grant all privilleges to user
• GRANT <privileges> ON <object name>
TO <grantee> [ <comma> <grantee> ... ]
[ WITH GRANT OPTION ]
• Create table u7.table8(id int);
• Grant Privileges on Functions/Procedures
• When dealing with functions and procedures, you
can grant users the ability to EXECUTE these
functions and procedures.
• Syntax
• GRANT EXECUTE ON object TO user;

• Create tablespace ts1 datafile ‘E:Oracle_lectsts1.dbf’ size
100M’
• ………………………………………………………….
• CREATE USER jward
• IDENTIFIED BY aZ7bC2
• DEFAULT TABLESPACE data_ts;
• GRANT connect TO jward;
• ........................................
• grant connect to craig;
• alter user craig quota unlimited on CRAIG_DATA;
• grant create table to craig;
• .................................
• create role rolename;
• grant connect to rolename;
• grant rollname to username;

Granting privileges
• GRANT
– Grants a privilege to a user
– Can grant privilege only if you have been granted
that privilege (or if you are the administrator)
grant <privilege> to <user>;
Grant create table to user_name with admin option

Examples of granting roles
• grant create table to john;
• grant all on CD_MASTER to tom;
• grant SELECT ON CD_MASTER.CD_NAME to
john;
• grant select, update on CD_DB to tom;
• grant references(CD_NO) on CD_DB to john;

Revoking roles
• REVOKE
– Revokes a privilege from a user
– Can revoke privilege only if you have been granted
that privilege (or if you are the administrator)
revoke <privilege> from <user>;

Dropping a Table
– All data and structure in the table are deleted.
– All indexes are dropped.
– All constraints are dropped.
– You cannot roll back the DROP TABLE
statement.
DROP TABLE dept80;
Table dropped.

Dropping a Table
• The general syntax is
DROP TABLE tablename [CASCADE CONSTRAINTS];
• For example,
DROP TABLE sample;
• Oracle displays a “Table dropped” message when a table is
successfully dropped.
• If you add optional CASCADE CONSTRAINTS clause, it removes
foreign key references to the table also.

• SELECT DISTINCT OBJECT_NAME FROM
USER_OBJECTS
• To find out what tables and sequences you
have defined use
SELECT tablespace_name,table_name
FROM user_tables
– The user_tables table is maintained by Oracle
– It has lots of columns, so don’t use
SELECT * FROM user_tables

• Select username from dba_users;
• select privilege
from dba_sys_privs
where grantee = 'RESOURCE':
•
PRIVILEGE
--------------------------------------
CREATE TYPE
CREATE TABLE
CREATE CLUSTER
CREATE TRIGGER
CREATE OPERATOR
CREATE SEQUENCE
CREATE INDEXTYPE
CREATE PROCEDURE

• select * from session_privs;
• PRIVILEGE ----------------------------------------
CREATE SESSION UNLIMITED TABLESPACE
CREATE TABLE

View Description
DBA_USERS Describes all users of the database
ALL_USERS Lists users visible to the current user, but does
not describe them
USER_USERS Describes only the current user

DDL(Data defination Language ) Using Oracle

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