An execution plan, basically, is the consequence of the query optimizer endeavor to ascertain the most proficient approach to implement the request represented by the SQL query you submitted. They are, in this way, the DBA's essential methods for investigating an ineffectively performing query. Instead of conjecture at why a given inquiry is performing a large number of outputs, putting your I/O through the rooftop, you can utilize the execution intend to distinguish the precise bit of SQL code that is causing the issue. For instance, it might filter a whole table-worth of information when, with the BEST possible list, it could basically backpack out just the row you need. This and more are shown in the execution plan. 

Despite the fact that SQL Server more often than not creates a decent arrangement, now and again it's not sufficiently brilliant to approve its arrangements and fix the poor ones. You can get an expected execution plan and a real graphical execution plan in SQL Server. PRODUCE these PLANS by utilizing the command ctrl M or ctrl L or by utilizing the symbols, which are put to one side of the execute symbol on the standard device bar of SQL Server Management Studio (SSMS).

There are two sorts of execution plans:

• Estimated execution plan: Estimated plans give an estimation of the WORK that the SQL server is required to perform to get the information.
• Actual execution plan: Actual execution plans are produced after the Transact-SQL questions or batches are executed. Along these lines, a real execution plan contains run time DATA, for example, the genuine resource usage metrics and any run time alerts.  You ought to always check the actual execution plan while investigating.