DDL (Data Definition Language) and DML (Data Manipulation Language) are two distinct subsets of SQL (Structured Query Language) that serve different purposes in managing databases. DDL is focused on the structure of the database, allowing developers to create, alter, or delete database objects such as tables, indexes, and schemas. Common DDL commands include CREATE, ALTER, and DROP. For instance, using the CREATE TABLE command, developers can define a new table along with its columns and data types, establishing the framework within which data will be stored.
On the other hand, DML is concerned with the actual data within those structures. It provides commands to manipulate the data contained in database tables. DML commands include operations like SELECT, INSERT, UPDATE, and DELETE. For example, a developer may use the INSERT INTO command to add new records to a table or the UPDATE command to modify existing data. Unlike DDL, which is about the schema and structure, DML directly interacts with the data itself, allowing for retrieval and modification as needed.
In summary, the key difference between DDL and DML lies in their functions within database management. DDL handles the creation and management of the database schema, setting the stage for where data will reside, while DML focuses on the operations applied to the data within those structures. Understanding these distinctions is essential for developers, as they often work with both aspects when designing and maintaining relational databases. This separation helps ensure that the database remains organized and that data can be efficiently manipulated when needed.