Robert Haas <robertmh...@gmail.com> wrote: > This says: > > Exclusion constraints ensure that that if any two rows are > compared on the specified column(s) or expression(s) using the > specified operator(s), not all of these comparisons will return > <literal>TRUE</>. > > I think that's backwards - the last clause should say "none of > those comparisons will return <literal>TRUE</>". > > Unless I'm confused. "not all" seems correct. For example, you could be checking the room number for equality and a range of time for overlap -- both must be TRUE to have a problem; otherwise you could only schedule one thing in the room for all time and one thing at a given time across all rooms. -Kevin
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