During the Comprehensive Database Performance Health Check, I often get the question about Estimated vs Actual Execution Plan. Today we are going to discuss differences and similarity between them.
Lots of people think that Estimated Executed Plan are not real and they change significantly when the actual execution plan is built. Actually, the estimated execution plan is always the plan which SQL Server would have used if we had run the query when the estimated plan was built.
I know lots of people usually do not believe the statement: Unless something big has not changed between running estimated plan and actual plan,