How to Drop a Column in PostgreSQL

DROP COLUMN is a metadata change. Postgres marks the column dropped and stops returning it, but the stored data stays in place until each row is rewritten by a later UPDATE or a VACUUM FULL. The statement is therefore fast even on huge tables, though disk is not freed right away. IF EXISTS makes it safe to re-run.

ALTER TABLE orders DROP COLUMN IF EXISTS internal_notes;

When views depend on it

Without CASCADE, Postgres refuses to drop a column that a view, index, or constraint depends on, and the error names the dependent object. CASCADE drops those objects too, which is quietly destructive: a view you had forgotten about disappears with no further prompt. Run the plain version first and read the error to see exactly what would go.

ALTER TABLE orders DROP COLUMN internal_notes CASCADE; -- drops dependent views too