How are SQL commands classified?

Question

Could someone tell me how are SQL commands classified?

Answer 1

SQL commands can be classified into different categories based on their purpose and functionality. Here are some common classifications of SQL commands:

1. Data Definition Language (DDL): DDL commands are used to define and manage the structure of database objects. They include commands such as CREATE, ALTER, and DROP, which are used to create, modify, and delete tables, indexes, views, and other database objects.

2. Data Manipulation Language (DML): DML commands are used to manipulate data within the database. The main DML commands are SELECT, INSERT, UPDATE, and DELETE. SELECT is used to retrieve data from the database, INSERT is used to add new records, UPDATE is used to modify existing records, and DELETE is used to remove records from tables.

3. Data Control Language (DCL): DCL commands are used to manage access and permissions within the database. These commands include GRANT, REVOKE, and DENY. GRANT is used to provide users with specific privileges or permissions, REVOKE is used to remove previously granted privileges, and DENY is used to explicitly deny permissions.

4. Transaction Control Language (TCL): TCL commands are used to manage transactions within the database. Transactions are sets of SQL statements that are executed as a single unit. The main TCL commands are COMMIT, ROLLBACK, and SAVEPOINT. COMMIT is used to permanently save changes made during a transaction, ROLLBACK is used to undo changes and restore the database to its previous state, and SAVEPOINT is used to mark a specific point within a transaction to which it can be rolled back.

These classifications help in understanding the purpose and functionality of different SQL commands, making it easier to use and manage databases effectively.

Answer 2

SQL has many commands which could be used to perform a set of tasks in a database, and even we could create a database using these commands in SQL. There are basically 4 categories into which SQL commands are classified. And they are:

1. DDL- Data Definition Language,
2. DQL- Data Query Language,
3. DML- Data Manipulation Language,
4. DCL- Data Control Language

Many other resources also point out the 5th category of SQL commands, and they are TCL- Transaction Control Language. If you wish to learn more about SQL or wish to get certified in SQL, check out the SQL training course from Intellipaat. Also, watch the following video on SQL Interview Questions and Answers and get started.

Answer 3

SQL commands can be classified into several categories based on their functionality and purpose. Here are the commonly recognized classifications of SQL commands:

1. Data Manipulation Language (DML) Commands: DML commands are used for managing and manipulating data within the database. They include:

   - SELECT: Retrieves data from one or more tables.

   - INSERT: Inserts new rows of data into a table.

   - UPDATE: Modifies existing data within a table.

   - DELETE: Removes rows of data from a table.

2. Data Definition Language (DDL) Commands: DDL commands are used to define and manage the structure of database objects. They include:

   - CREATE: Creates new database objects such as tables, views, indexes, or schemas.

   - ALTER: Modifies the structure of existing database objects.

   - DROP: Deletes database objects such as tables, views, or indexes.

   - TRUNCATE: Removes all data from a table, but keeps the structure intact.

3. Data Control Language (DCL) Commands: DCL commands are used to manage the security and permissions within the database. They include:

   - GRANT: Provides users with specific privileges or permissions.

   - REVOKE: Removes or denies previously granted privileges.

4. Transaction Control Commands: Transaction control commands are used to manage transactions within the database. They include:

   - COMMIT: Saves all changes made within a transaction.

   - ROLLBACK: Reverts all changes made within a transaction.

   - SAVEPOINT: Sets a savepoint within a transaction, allowing partial rollbacks.

5. Data Query Language (DQL) Commands: Although not an official category, DQL is often used to refer to commands that primarily retrieve data. The main DQL command is:

   - SELECT: Retrieves data from one or more tables.

These classifications help organize SQL commands based on their intended purpose and functionality, making it easier to understand and work with SQL databases.

Answer 4

SQL commands are commonly classified into the following categories:

1. Data Definition Language (DDL): DDL commands are used to define and manipulate the structure of database objects. Some common DDL commands include:

- CREATE: Creates a new database, table, index, or view.

- ALTER: Modifies the structure of an existing database object.

- DROP: Deletes a database, table, index, or view.

- TRUNCATE: Removes all data from a table.

2. Data Manipulation Language (DML): DML commands are used to retrieve, insert, update, and delete data within database objects. Some common DML commands include:

- SELECT: Retrieves data from one or more tables.

- INSERT: Adds new rows of data into a table.

- UPDATE: Modifies existing data within a table.

- DELETE: Removes rows of data from a table.

3. Data Control Language (DCL): DCL commands are used to control access and permissions within the database. Some common DCL commands include:

- GRANT: Provides users with specific privileges and permissions.

- REVOKE: Removes previously granted privileges from users.

4. Transaction Control Language (TCL): TCL commands are used to manage transactions within the database. Some common TCL commands include:

- COMMIT: Saves changes made within a transaction.

- ROLLBACK: Reverts changes made within a transaction.

- SAVEPOINT: Sets a point within a transaction to which it can be rolled back.

These classifications help in understanding the purpose and functionality of different SQL commands and how they can be used to interact with a database.