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AskSQLTeam
Ask SQLTeam Question
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 Posted - 2002-03-11 : 00:41:11
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| Phil writes "I have a table that contains an optional field which, if specified, must be unique and which is also used as an index into the table. In previous databases I have worked with this was simply defined as a unique secondary key "ignoring nulls".Is there any way of doing this in SQL Server 7 (or 2000)? The closest I can find in the documentation is the UNIQUE CONSTRAINT which allows one record to contain a null value (which seems pretty pointless) but nothing that will ignore multiple null values and enforce uniqueness on non-null values.Obviously I can achieve a similar effect with a trigger, but would prefer to avoid that if possible." |
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Sparsely-Populated Unique Indexes