Q2: What are DDL, DML, DCL, TCL, and DQL in SQL?
SQL statements are categorized into five sublanguages based on operational scope:
- DDL (Data Definition Language): Defines and alters schema structures. Commands:
CREATE,ALTER,DROP,TRUNCATE,RENAME. - DML (Data Manipulation Language): Modifies stored data rows. Commands:
INSERT,UPDATE,DELETE,MERGE. - DQL (Data Query Language): Retrieves records from schemas. Command:
SELECT. - DCL (Data Control Language): Manages permissions and administrative privileges. Commands:
GRANT,REVOKE. - TCL (Transaction Control Language): Manages atomic transactional changes. Commands:
COMMIT,ROLLBACK,SAVEPOINT.
Key Takeaways
- DDL alters schema metadata; DML and DQL operate directly on table data rows.
- TCL manages state persistence across transactions; DCL enforces security permissions.