This is very basic question asked by some interviewers. We can split SQL into these five areas.
It mainly and solely contains "SELECT" statement. SELECT is concerned simply with retrieving data stored in database. It has optional clauses and tweaks.
It is concerned about manipulation of data within database. DML consists of four commonly used statements: INSERT, UPDATE, DELETE and MERGE.
|INSERT||Insert new records in table.|
|UPDATE||Updates existing records within table.|
|DELETE||Deletes records within tables.|
|MERGE||It's like upsert operation. It performs both insert and update operation based of condition.|
The primary purpose of DDL is to create, modify or remove tables and other objects such as stored procedures, functions, triggers; from the database. It consists of variations of CREATE, ALTER and DROP statements.
|CREATE||It creates SQL objects like stored procedures, tables, columns, etc.|
|ALTER||It modifies existing SQL objects.|
|DROP||Deletes existing objects.|
It's for restrict access to tables and database objects. It's composed of various GRANT and REVOKE statements that allow or deny user access to database objects.
|GRANT||Allows users to read/write on certain objects.|
|REVOKE||Denies user to access specific objects.|
TCL is concerned about initiating, committing or rolling back of transaction. A transaction is basically unit of work performed by server. It's main purpose is to maintain integrity of data within SQL statements. It contains statements like BEGIN TRANSACTION, COMMIT and ROLLBACK.
|BEGIN TRANSACTION||Opens a transaction.|
|COMMIT||Indicates transaction is completed. Closes transaction.|
|ROLLBACK||ROLLBACK a transaction in case of error.|