VACUUM
VACUUM is a SQL statement in the PostgreSQL Specific category. PostgreSQL maintenance: VACUUM reclaims storage from deleted/updated rows. ANALYZE updates statistics. The syntax is VACUUM [FULL] [ANALYZE] [table_name];. It returns maintenance completed. A typical example: VACUUM ANALYZE employees; -- Reclaims storage and updates query statistics VACUUM FULL employees; -- More aggressive: rewrites table to reclaim space (locks table) AUTOVACUUM: -- PostgreSQL automatically vacuums based on activity thresholds A close relative is SERIAL, which postgreSQL auto-increment type. Creates an INTEGER column with a sequence. Equivalent to AUTO_INCREMENT in MySQL. A close relative is RETURNING, which postgreSQL extension that returns values from INSERT/UPDATE/DELETE statements (like OUTPUT in SQL Server). A close relative is ARRAY, which postgreSQL supports array columns and array operations. Can be multi-dimensional. More about this category: PostgreSQL-specific features — SERIAL, RETURNING, ARRAY, JSONB, UPSERT. Related PostgreSQL Specific entries: SERIAL, RETURNING, ARRAY, JSONB, UPSERT (INSERT ON CONFLICT), ILIKE, BIGSERIAL / SMALLSERIAL, GENERATED AS IDENTITY.