DML – Data Manipulation Language
They are SQL statements which works with Data in a database. Using them you can insert, retrieve, store, delete, modify and update data.
Example : INSERT, UPDATE, DELETE statements
INSERT – Insert data into table
UPDATE – Modify existing records
DELETE – Delete records from table
DDL – Data Definition Language
These statements works with the structure of database objects like tables or schemas. Using them you can Create, Modify or Drop table, database or schema.
Examples: CREATE, ALTER, DROP statements
CREATE – Create new Database, Table or Schema
ALTER – Modify existing table by adding, deleting, renaming or modifying column definition
DROP – Delete existing Database, Table or Schema
DCL – Data Control Language
These statements are used to control access to database by creating roles, granting them permissions or withdrawing users access privileges.
Example : GRANT, REVOKE
GRANT – Giving permission to users for certain database objects
REVOKE – Removing / withdrawing permissions from users which are previously granted.
TCL – Transaction Control Language
These are the statements which are used to control/ manage the Transactions in a database
Example : COMMIT, ROLLBACK, SAVEPOINT, SET TRANSACTION
SET TRANSACTION – set the behaviour or characteristics of a transaction
COMMIT – Ensure that the statements from start till this point is
ROLLBACK – Undo all changes if any error occurs in a Transaction
SAVEPOINT – A named point within a Transaction, helpful when only a part of transaction needs to rollback.
DQL – Data Query Language
These statements are used to Query data from database.
Example : SELECT
SELECT – Retrieve data from database.