On Thu, 20 Jan 2005, Alex wrote: > i have a unique index on a table over multiple columns. If now one of > the records has a null value in one of the indexed columns i can insert > the same record multiple times. > > Is this a problem within postgres or expected? Expected. NULLs are effectively not considered as the same for the purposes of UNIQUE. The predicate basically functions as: 2) If there are no two rows in T such that the value of each column in one row is non-null and is equal to the value of the cor- responding column in the other row according to Subclause 8.2, "<comparison predicate>", then the result of the <unique predi- cate> is true; otherwise, the result of the <unique predicate> is false. ---------------------------(end of broadcast)--------------------------- TIP 4: Don't 'kill -9' the postmaster
