What is the difference between DELETE and TRUNCATE?

DELETE is a DML operation with a WHERE clause. It removes rows one by one logically, can fire row-level triggers, and is fully transactional in most engines. TRUNCATE is a fast bulk operation that deallocates pages instead of visiting every row.

DELETE FROM sessions
WHERE expires_at < now();

TRUNCATE TABLE staging_events;

Key differences

• DELETE supports WHERE and can remove a subset; TRUNCATE removes all rows
• DELETE fires row-level delete triggers; TRUNCATE usually does not
• TRUNCATE takes a stronger lock and can block concurrent readers or writers
• TRUNCATE is much faster on large tables because it does not scan row by row
• TRUNCATE often resets identity or sequence state; DELETE does not
• TRUNCATE may be blocked by foreign key references in some engines
• Both can be rolled back in PostgreSQL, but behavior varies by database

Use DELETE when you need row predicates, triggers, or fine-grained control. Use TRUNCATE for staging tables, test resets, or bulk cleanup where removing everything is intended and the locking impact is acceptable.