SQL Overview

SQL Overview
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SQL Overview :-

These commands can be classified into the following groups based on their nature.

DDL - Data Definition Language
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1 CREATE :- Creates a new table, a view of a table, or other object in the database.

2 ALTER :- Modifies an existing database object, such as a table.

3 DROP :- Deletes an entire table, a view of a table or other objects in the database.



Ex:-

CREATE TABLE XXSD_TEST_TL(
EMP_NO VARCHAR2(10),
EMP_NAME VARCHAR2(100),
SALARY NUMBER
)

select * from XXSD_TEST_TL


ALTER TABLE XXSD_TEST_TL  ADD ( DOB DATE)

DROP TABLE XXSD_TEST_TL

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DML - Data Manipulation Language
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1 SELECT :- Retrieves certain records from one or more tables.

2 INSERT :- Creates a record.

3 UPDATE :- Modifies records.

4 DELETE :- Deletes records.

Ex:-

select * from XXSD_TEST_TL

Insert into XXSD_TEST_TL values( 'A123','Sunil','20000')

commit;

UPDATE XXSD_TEST_TL
set EMP_NAME = 'Rakesh'
where EMP_NO = 'A123'

commit;

DELETE FROM XXSD_TEST_TL
where EMP_NO = 'A123'

commit;

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DCL - Data Control Language
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1 GRANT :- Gives a privilege to user.

2 REVOKE :- Takes back privileges granted from user.

Ex:-


select * from XXSD_TEST_TL


GRANT SELECT ON XXSD_TEST_TL TO XXSD

REVOKE SELECT ON XXSD_TEST_TL FROM XXSD