What do you mean by DDL, DML, DCL and TCL? Explain

DDL, DML, DCL, and TCL are types of SQL (Structured Query Language) commands. SQL is a standard language for managing data held in a relational database management system.

1. DDL (Data Definition Language): DDL is used to define the structure that holds the data. For example, to create, alter, truncate, and drop database and tables. DDL is not used to manipulate data itself.

   • CREATE: To create databases and database objects.
   • ALTER: To alter existing database objects.
   • DROP: To drop databases and databases objects.
   • TRUNCATE: To remove all records from a table, including all spaces allocated for the records are removed.

2. DML (Data Manipulation Language): DML is used for adding (inserting), deleting, and modifying (updating) data in a database.

   • SELECT: To select specific data from a database.
   • INSERT: To insert new data into a database.
   • UPDATE: To update existing data within a database.
   • DELETE: To delete records from a database.

3. DCL (Data Control Language): DCL is used to control access to data within the database. These commands are used to implement security on database objects.

   • GRANT: To grant specific user to perform specific task.
   • REVOKE: To take back permissions from the user.

4. TCL (Transaction Control Language): TCL commands deal with the transaction operations within databases.

   • COMMIT: To write and store the changes to the database.
   • ROLLBACK: To restore the database to the original since the last COMMIT.
   • SAVEPOINT: Creates points within groups of transactions in which to ROLLBACK.
   • SET TRANSACTION: Places a name on a transaction.