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What are the difference between DDL, DML and DCL commands? 
DDL is Data Definition Language statements. Some examples: 
CREATE - to create objects in the database 
ALTER - alters the structure of the database 
DROP - delete objects from the database 
TRUNCATE - remove all records from a table, including all spaces allocated 
for the records are removed 
COMMENT - add comments to the data dictionary 
GRANT - gives user's access privileges to database 
REVOKE - withdraw access privileges given with the GRANT command 
DML is Data Manipulation Language statements. Some examples: 

SELECT - retrieve data from the a database 
INSERT - insert data into a table 
UPDATE - updates existing data within a table 
DELETE - deletes all records from a table, the space for the records remain 
CALL - call a PL/SQL or Java subprogram 
EXPLAIN PLAN - explain access path to data 
LOCK TABLE - control concurrency 
DCL is Data Control Language statements. Some examples: 

COMMIT - save work done 
SAVEPOINT - identify a point in a transaction to which you can later roll 
back 
ROLLBACK - restore database to original since the last COMMIT 
SET TRANSACTION - Change transaction options like what rollback segment to 
use 
 
 
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