What is DBMS Queries ?

SQL Commands

  • SQL commands are instruction which is used to communicate with the database.
  • It is also used to perform specific tasks, functions, and queries of data
  • It can also perform various tasks like creating a table, updating a table, deleting a table etc.

Types of SQL Commands

There are 5 types of SQL Commands

DDL (Data Definition Language)

  • Changing the structure of table like creating table, altering a table, and deleting a table can be done using this DDL
  • Commands in ddl are autocommitted which means it permanently save all changes in the database.
  • Some of the command in DDL are: create, alter,drop, truncate.

DML – Data Manipulation Language

  • These commands are used for modifing the database. Responsible for all form of changes in the database.
  • Commands in dml are not autocommitted which means it cannot permanently save all changes in the database. They can roll back.
  • Some of the commands under DML are:
  • Insert, Update, Delete.

DCL – Data Control Language

  • These command are used to grant and revoke authorities from user.
  • Some of the commands under DCL are:
  • Grant
  • Revoke

TCL – Transaction Control Language

  • These commands can only be used with DML commands like Insert, delete, update etc.
  • These operations are auto committed that is why they cannot be used while creating tables or dropping them.
  • Some of the commands under TCL are:
    • Commit
    • Roll Back
    • Save Point

DQL – Data Query Language

  • These commands are used to fetch the data from a database.
  • Select is the only command used in this language.

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