What are DDL and DML, and how do they work within SQL?

Data Definition Language (DDL) and Data Manipulation Language (DML) in SQL

Ever encountered the terms “DDL” and “DML” in the context of a database but not quite sure what they mean? This article will clarify these concepts, explain their role and how they relate to SQL.

Data Definition Language (DDL)

DDL is used to handle the structure and design of the database. It allows you to create, modify, and manage database objects such as tables, views, indexes, stored procedures, and functions. Some common DDL commands include:

• CREATE: is used to create database objects.
• ALTER: Modify the structure of an existing database object.
• DROP: Delete database objects.
• TRUNCATE: Delete all records in the table, including allocated space.

Data Manipulation Language (DML)

DML focuses on the actual data in the database. It allows you to manipulate and manage data by:

• SELECT: Retrieve data from the table.
• INSERT: Adds a new record to the table.
• UPDATE: Modifies existing records in the table.
• DELETE: Delete a record from the table.
• MERGE: Combines insert and update operations.

Relationship with SQL

DDL and DML are both subsets of SQL (Structured Query Language), a powerful database language. SQL statements can be divided into these two types based on their purpose. DDL statements are used to define the database structure, while DML statements are used to manipulate the data in it.

Other types

In addition to DDL and DML, there are other types of SQL commands that play an important role in database management:

• Data Control Language (DCL): Manage access rights and privileges.
• Transaction Control Language (TCL): Controls and manages database transactions.

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