Not long ago, I ran into a performance issue: a stored procedure that was taking about 30 seconds to execute. For a database handling thousands of requests, this was unacceptable. The culprit? A seemingly innocent LEFT JOIN combined with an IS NULL condition. While this approach worked functionally, it was far from optimal, especially given the size of the tables involved. After some investigation and experimentation, I discovered that replacing the LEFT JOIN + IS NULL with a NOT EXISTS clause drastically improved performance. In this article, I’ll walk you through the problem, the solution, and the key takeaways so you can apply this optimization in your own…
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