Avoid using NOT IN whilst comparing nullable columns. Use NOT EXISTS instead.
When NOT IN is used in a query, SQL Server compares each result to null (even if no rows are returned). NOT EXISTS does not perform a comparison with nulls.
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Home » Tip: T-SQL Performance–NOT IN vs NOT EXISTS
Avoid using NOT IN whilst comparing nullable columns. Use NOT EXISTS instead.
When NOT IN is used in a query, SQL Server compares each result to null (even if no rows are returned). NOT EXISTS does not perform a comparison with nulls.
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