SQL Server Execution Plans - Red Gate Software

Figure 5.23
Chapter 5: Controlling Execution Plans with Hints
With a full knowledge of your system that you have from examining the indexes and
statistics on the tables, you know that the plan for the second query should be completely
different because the value passed (288) is much more selective and a useful index exists
on that column. So, you modify the queries using the RECOMPILE hint. In this instance
(Listing 5.25) I'm adding it to both queries so that you can see that the performance gain
in the second query is due to the RECOMPILE and the subsequent improved execution
plan, while the same RECOMPILE on the first query leads to the original plan.
DECLARE @PersonId INT = 277;
SELECT soh.SalesOrderNumber ,
soh.OrderDate ,
soh.SubTotal ,
soh.TotalDue
FROM Sales.SalesOrderHeader soh
WHERE soh.SalesPersonID = @PersonId
OPTION ( RECOMPILE );
SET @PersonId = 288;
SELECT soh.SalesOrderNumber ,
soh.OrderDate ,
soh.SubTotal ,
soh.TotalDue
FROM Sales.SalesOrderHeader soh
WHERE soh.SalesPersonID = @PersonId
OPTION ( RECOMPILE );
Listing 5.25
207