SQL DDL Commands Explained: CREATE, ALTER, DROP, and TRUNCATE

Data Definition Language (DDL) is the set of SQL commands used to define and modify database structure, including creating tables, altering columns, and removing objects. The CREATE TABLE command builds new tables with defined columns, data types, and constraints such as primary keys and unique values. ALTER TABLE is widely used in database migrations to add, remove, or rename columns as a system evolves over time. DROP TABLE permanently deletes a table along with all its data and cannot be undone, making backups essential in production environments. TRUNCATE TABLE clears all records from a table while preserving its structure, and is significantly faster than a DELETE statement on large tables but does not trigger database triggers.