SQL Command Types

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


• RENAME - raname column for a table


• COMMENT - add comments to the data dictionary

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

TCL is Transaction 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

DQL/DRL is Data Query/Retrieve Language statements. Some examples:

• SELECT - retrieve data from the a database

DCL is Data Control Language statements. Some examples:

• GRANT - gives user's access privileges to database


• REVOKE - withdraw access privileges given with the GRANT command


• DENY - remove user's access privileges to database