Categories of SQL Commands

Introduction

SQL (Structured Query Language) is a standard language for managing and manipulating databases. It is used to perform tasks such as update data on a database, or retrieve data from a database. The SQL commands are divided into several categories based on their functionality.

Data Manipulation Language (DML) Commands

DML commands are used for managing data within schema objects. The primary commands under this category include:

1. SELECT: This command is used to select specific data from a database.
2. INSERT: This command is used to insert new data into a database.
3. UPDATE: This command is used to update existing data within a database.
4. DELETE: This command is used to delete records from a database.

Data Definition Language (DDL) Commands

DDL commands are used for defining and modifying database schema. The primary commands under this category include:

1. CREATE: This command is used to create databases and tables.
2. ALTER: This command is used to alter (modify) the database structure.
3. DROP: This command is used to delete tables and databases.

Data Control Language (DCL) Commands

DCL commands are used for controlling access to data within the database. The primary commands under this category include:

1. GRANT: This command is used to provide user access to the database.
2. REVOKE: This command is used to take back the access granted to the user.

Transaction Control Language (TCL) Commands

TCL commands are used to manage transactions within the database. The primary commands under this category include:

1. COMMIT: This command is used to save all changes made in the transaction to the database.
2. ROLLBACK: This command is used to undo the changes made in the transaction.

Real-world Applications and Examples

SQL commands are widely used in various real-world scenarios. For instance, the SELECT command is used to retrieve specific data from a database, while the INSERT command is used to add new data to a database. Similarly, the UPDATE command is used to modify existing data in a database, and the DELETE command is used to remove data from a database.

Advantages and Disadvantages of SQL Commands

SQL commands offer several advantages, such as ease of use, standardization, and versatility. However, they also have some disadvantages, such as complexity and potential for data manipulation.

Conclusion

In conclusion, SQL commands are essential tools for managing and manipulating databases. They are divided into several categories based on their functionality, and each category has its own set of commands.

Summary

SQL commands are divided into several categories based on their functionality. These include Data Manipulation Language (DML) commands, Data Definition Language (DDL) commands, Data Control Language (DCL) commands, and Transaction Control Language (TCL) commands. Each category has its own set of commands that are used for specific tasks such as managing data within schema objects, defining and modifying database schema, controlling access to data within the database, and managing transactions within the database.

Analogy

Think of a database as a library and SQL commands as the librarian. The librarian (SQL commands) has different tasks like adding new books (INSERT), updating the information of existing books (UPDATE), removing old books (DELETE), creating new sections (CREATE), modifying the structure of the library (ALTER), granting or revoking access to library members (GRANT/REVOKE), and managing transactions (COMMIT/ROLLBACK).