What is Sql commands, DDL ,DML ,TCL ,DCL ,DRL

1. INTRODUCTION TO SQL
Prepared by
Ravichandiran
Senior Oracle Trainer

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Trainers.
• Oracle unique id for students
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preparation.

3. COMMANDS
DDL - DATA DEFINITION LANUGAGE
DML - DATA MANIPULATION LANGUAGE
TCL - TRANSACTION CONTROL LANGUAGE
DCL - DATA CONTROL LANGUAGE
DRL - DATA RETRIEVAL LANGUAGE

4. DDL
• Used to create or modify the structure of the table.
• Auto commit occurs. Changes cannot be rolled
back.
• Session independent commands.
• Commands are :
CREATE, ALTER DROP, TRUNCATE, RENAME

5. DDL - CREATE
SYNTAX
create table <tab_name>
(
col1 datatype(size),
col2 datatype(size),
...........
.............
coln datatype(size)
);
SYNTAX
create table <tab_name>
(
col1 datatype(size),
col2 datatype(size),
...........
.............
coln datatype(size)
);
EXAMPLE
Create table emp
(
empno number(5),
ename varchar2(20),
job varchar2(20)
);
EXAMPLE
Create table emp
(
empno number(5),
ename varchar2(20),
job varchar2(20)
);

6. DDL - ALTER
ADD
• ALTER TABLE EMP ADD
DOJ DATE;
• ALTER TABLE EMP ADD
( SALARY NUMBER(5),
COMM NUMBER(4),
DEPTNO NUMBER(3));
ADD
• ALTER TABLE EMP ADD
DOJ DATE;
• ALTER TABLE EMP ADD
( SALARY NUMBER(5),
COMM NUMBER(4),
DEPTNO NUMBER(3));
MODIFY
• ALTER TABLE EMP ADD
DOJ DATE;
• ALTER TABLE EMP ADD
( SALARY NUMBER(5),
COMM NUMBER(4),
DEPTNO NUMBER(3));
MODIFY
• ALTER TABLE EMP ADD
DOJ DATE;
• ALTER TABLE EMP ADD
( SALARY NUMBER(5),
COMM NUMBER(4),
DEPTNO NUMBER(3));

7. DDL - ALTER
DROP COLUMN
• ALTER TABLE EMP DROP
COLUMN DEPTNO;
• ALTER TABLE EMP
DROP(DOJ,COMM);
DROP COLUMN
• ALTER TABLE EMP DROP
COLUMN DEPTNO;
• ALTER TABLE EMP
DROP(DOJ,COMM);
RENAME COLUMN
• ALTER TABLE EMP
RENAME COLUMN EMPNO
TO ENO;
RENAME COLUMN
• ALTER TABLE EMP
RENAME COLUMN EMPNO
TO ENO;

8. DDL - DROP
TABLE DROPPED
• DROP TABLE EMP;
• DROP TABLE EMP
PURGE;
• PURGE RECYCLEBIN;
• PURGE TABLE EMP;
TABLE DROPPED
• DROP TABLE EMP;
• DROP TABLE EMP
PURGE;
• PURGE RECYCLEBIN;
• PURGE TABLE EMP;
FLASHBACK COMMAND
• Flashback table emp to
before drop;
• Flashback table emp to
before drop rename to
employees;
FLASHBACK COMMAND
• Flashback table emp to
before drop;
• Flashback table emp to
before drop rename to
employees;

9. DDL - TRUNCATE
• Used to remove records from table.
• Cannot delete single row alone
• Changes are permanent. So deleted record cannot
be rolled back.
TRUNCATE TABLE EMP;

10. DDL - RENAME
• Used to rename the table.
RENAME <OLD_TABLE_NAME> TO
<NEW_TAB_NAME>;
RENAME EMP TO EMPLOYEES;