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

DDL and DML in database management: Detailed explanation of core concepts

Database operations are mainly divided into two categories: data definition language (DDL) and data manipulation language (DML). This article will delve into the specifics of both and their importance in database management.

Data Definition Language (DDL)

DDL commands focus on the structure and definition of the database itself, including tables, constraints, and relationships. Major DDL operations include:

• CREATE: Create new databases, tables, indexes, and other database objects.
• ALTER: Modify existing database structures, such as table definitions or column properties.
• DROP: Delete a database object, effectively clearing the data in the table or deleting the entire table or database.
• TRUNCATE: Clears the data in the table but does not delete the table's structure or allocated space.
• COMMENT: Add description and metadata to the database dictionary.
• RENAME: Adjust the names of database objects to improve organization.

Data Manipulation Language (DML)

DML commands interact directly with data in the database. They enable users to:

• SELECT: Retrieve data from one or more tables based on specified criteria.
• INSERT: Adds new records or data to the table.
• UPDATE: Changes existing data in the table.
• DELETE: Delete records or data from a table.
• MERGE: Combine insert and update operations to modify data efficiently.
• CALL: Execute a stored procedure or Java subroutine.
• EXPLAIN PLAN: The best data access path for analysis queries.
• LOCK TABLE: Controls concurrent database access to prevent conflicts.

Other notes

In addition to DDL and DML, databases use Data Control Language (DCL) to manage user permissions and access rights. Transaction Control Language (TCL) is used to create, manage, and control database transactions.

Understanding the difference between DDL and DML is essential for proper database management. DDL operations shape the database infrastructure, while DML operations control the manipulation and retrieval of data within these structures. Together, they form the basis for efficient database operations and ensure data integrity and accessibility.

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