SQL SERVER – Optimize Key Lookup by Creating Index with Include Columns

I love query tuning and performance tuning projects. In one of the recent Comprehensive Database Performance Health Check my client had a very interesting scenario where their queries were running pretty fast earlier but gradually started to run slow and eventually started to take over 10 minutes to execute. They reached out to me to tune their slow running query. While looking at the query execution plan, there is a big key lookup operation which was actually slowing down their query. I decided to create an index with include column on that table and resolve this issue.

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