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Explain SQL subcategories giving at least one example in each category. |
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Answer» SQL commands can be classified into following categories: (i) Data Definition Language(DDL): They are used to define the structure of tables and other objects in a database. For example: CREATE, ALTER, DROP, TRUNCATE, RENAME. (ii) Data Manipulation Language(DML): They are used to manipulate and access the data in the database. For Example: SELECT, INSERT, UPDATE, DELETE, LOCK TABLE. (iii) Transaction Control Language(TCL): Used to manage transactions in the database. They are also used to manage the changes done by DML statements. For Example: COMMIT, SAVEPOINT, ROLLBACK, SET TRANSACTION. (iv) Data Control Language(DCL): These commands are often used by Database Administrators and are considered as expert level commands because they are used to assign security levels in a database. Also, they are used to grant and define role and access privileges to the users. For Example: GRANT, REVOKE. |
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