The purpose of DDL language is to define the data structure of the database which includes –  Create database, schema or table.  Alter the tables and table fields.  Drop the database, schema, table, and table fields.  Truncate a table.  The purpose of DML language is to perform any manipulation in the database which includes –  Select the data from the database.  Insert new records in the table.  Update any existing record in the table.  Delete the table records.  The purpose of DCL language is to control user permissions in a database like –  Grant permission to a user to access the database or revoke permission of an already existing user.  Grant user-restricted permission like read-only, read and write by allowing the user to run only specific SQL commands on the database.  Revoke any existing set of rules or permission granted to a user.  The purpose of TCL language is to manage transactions in a database where COMMIT is used to permanently save changes made by the current transaction and ROLLBACK to undo the changes made by the current transaction. For example, the usage of TCL commands can be noticed in digital payments where the payee can reverse a transaction.