Execution plan of a server query. As you can see in the above execution plan, SQL Server has highlighted a missing index that it thinks would help our query improve.

SQL Server has an optimizer that usually does a great job of optimizing code for the most effective execution. A query execution plan is the breakdown of how the optimizer will run (or ran) a query.

Finally, the other major area of memory (in SQL Server) is known as the execution plan cache, which stores the compiled order of operations the database uses to return the results of your queries.