ALTER TABLE proposalsADD CONSTRAINT one_draft_eachCHECK (draft IS false) OR (draft IS true AND user_id NOT IN (SELECT user_id FROM proposals WHERE draft IS true)) It will be a lot slower than a UNIQUE constraint, especially as your table gets bigger...
On Thu, 2007-04-19 at 10:52 +0100, Nathaniel wrote:
ALTER TABLE proposals ADD CONSTRAINT one_draft_each CHECK draft IS
false OR UNIQUE user_id
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