Back to course

Introduction to SQL: DDL, DML, and DCL

Database Fundamentals: From Zero to Hero

Lesson 13: Introduction to SQL: DDL, DML, and DCL

SQL (Structured Query Language) is the standard language used to communicate with and manage relational databases. It is not a programming language but a declarative language.

Categories of SQL Commands

SQL commands are broadly categorized into three main groups:

1. DDL: Data Definition Language

DDL commands are used to define the database schema—the structure that holds the data. They affect the organization of tables and objects.

  • Commands:
    • CREATE: To create databases, tables, indexes, or views.
    • ALTER: To modify the structure of an existing object (e.g., add a column).
    • DROP: To completely remove an object (table, view, index) from the database.

2. DML: Data Manipulation Language

DML commands are used to interact with the data stored within the tables. This is what you will use most often.

  • Commands:
    • SELECT: To retrieve data from the database (the most common command).
    • INSERT: To add new records (rows) to a table.
    • UPDATE: To modify existing records.
    • DELETE: To remove records (rows) from a table.

3. DCL: Data Control Language

DCL commands are used to control access and permissions for users.

  • Commands:
    • GRANT: To give specific access permissions to a user.
    • REVOKE: To take away permissions.

Focus: We will spend the next several lessons mastering DML, particularly the powerful SELECT statement.