What's the Difference Between DDL and DML in SQL Database Management?

Understanding DDL and DML in SQL Database Management

SQL, the cornerstone of database management, utilizes various command types, primarily categorized as DDL, DML, DCL, and TCL. This article focuses on the core functionalities of DDL and DML, which are fundamental to defining and manipulating database structures and data.

Data Definition Language (DDL): Shaping the Database Structure

DDL, or Data Definition Language, is responsible for creating and managing the database schema. Its commands enable the creation, modification, and deletion of database objects, including tables, indexes, views, stored procedures, functions, and triggers.

Key DDL Commands:

• CREATE: Used to build new databases and their constituent elements.
• ALTER: Modifies the structure of existing database objects.
• DROP: Removes database objects.
• TRUNCATE: Deletes all data from a table, reclaiming allocated space.
• COMMENT: Adds descriptive annotations to the database dictionary.
• RENAME: Changes the name of a database object.

Data Manipulation Language (DML): Working with Database Data

DML, or Data Manipulation Language, handles the manipulation of data within the database. Its commands allow for retrieving, adding, modifying, and removing data stored in tables.

Essential DML Commands:

• SELECT: Retrieves data from one or more tables.
• INSERT: Adds new records to a table.
• UPDATE: Modifies existing records in a table.
• DELETE: Removes records from a table.
• MERGE: Performs simultaneous insert and update operations.
• CALL: Executes stored procedures or Java subprograms.
• EXPLAIN PLAN: Analyzes data access paths for optimization.
• LOCK TABLE: Controls concurrent access to tables.

The above is the detailed content of What's the Difference Between DDL and DML in SQL Database Management?. For more information, please follow other related articles on the PHP Chinese website!