Summary
union/unionAll exist as trivial text appenders; intersect/except/exceptAll are absent. Adding them mirrors the existing union methods almost verbatim (Postgres/SQLite native; MySQL 8.0.31+ for INTERSECT/EXCEPT, else document the gap).
Effort: S. Location: src/client.ts:~4474. (Note: fix the union param-merging bug #1029 first so the new ones don't inherit it.) Found via internal code audit.