Swapna Kumar Panda

Swapna Kumar Panda

08-11-2022

11:45

SQL Commands, explained ➤ DDL ➤ DML ➤ DQL ➤ DCL ➤ TCL ⇩

Introduction to SQL ⬘ SQL stands for Structured Query Language. ⬗ SQL is a computer language for storing, manipulating, and retrieving data in a relational database. ⬙ SQL provides useful commands for performing these operations. ⬖ These commands are put into 5 categories

➊ DDL DDL ➟ Data Definition Language ⬘ DDL commands are used to define the database schema. ⬗ DDL is a set of SQL commands that are used to create, modify, and delete database structures but not data.

⬙ List of DDL Commands ➤ CREATE Used to create the database or its objects (like Table, Views, Stored Procedures, Index, etc.) ➤ DROP Used to delete objects from the database. ➤ ALTER Used to alter the structure of the database.

➤ TRUNCATE Used to remove all records from a table, including all spaces allocated for the records. ➤ RENAME Used to rename an object already existing in the database. ➤ COMMENT Used to add comments to the data dictionary.

➋ DML DML ➟ Data Manipulation Language ⬘ DML commands are used to manipulate the data present in the database. ⬙ List of DML Commands ➤ INSERT Used to insert data into a table. ➤ UPDATE Used to update existing data within a table.

➤ DELETE Used to delete records from a database table. ➤ LOCK Used to control the concurrency on a table. ➤ CALL Used to call a PL/SQL code. ➤ EXPLAIN PLAN To describe the access path to data.

➌ DQL DQL ➟ Data Query Language ⬘ DQL commands are used for performing queries on the data within schema objects. ⬙ List of DQL Commands ➤ SELECT Used to retrieve data from the database.

➍ DCL DCL ➟ Data Control Language ⬘ DCL commands mainly deal with the rights, permissions, and other controls of the database system. ⬙ List of DCL Commands ➤ GRANT To give users access privileges to the database. ➤ REVOKE To withdraw the user’s access privileges.

➎ TCL TCL ➟ Transaction Control Language ⬘ TCL commands deal with the transaction within the database.

⬙ List of TCL Commands ❍ COMMIT Used to commit a transaction. ➤ ROLLBACK Used to rollback a transaction in case of any error occurs. ➤ SAVEPOINT Used to set a savepoint within a transaction. ➤ SET TRANSACTION Used to specify characteristics for the transaction.

🏁 Final Words ⬘ We saw how SQL uses certain commands to carry out the required task. ⬙ We categorized all commands into 5 categories. Let's summarize all these in a diagram.

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