4.5Discovering Existing Constraints

-- List all constraints on a table (PostgreSQL)
SELECT con.conname, con.contype, pg_get_constraintdef(con.oid)
FROM pg_constraint con
JOIN pg_class rel ON rel.oid = con.conrelid
WHERE rel.relname = 'users';

-- contype: p = primary key, f = foreign key, u = unique, c = check