SQL Commands:
1. DDL Commands (data definition language)A. CREATE
B. TRUNCATE
C. ALTER
D. RENAME
E. DROP
2. DML Commands (Data Manipulation language)
A. INSERT
B. UPDATE
C. DELETE
3. DCL Commands (Data control language)
A. GRANT
B. REVOKE
4. TCL commands (Transaction control language)
A. COMMIT
B. ROLLABCK
C. SAVEPOINT
5. DRL command (Data Retrieval language)
A. SELECT
Note: all commands except select are physical command means they effect database,
select is a logical command and it not affect database.
