Write a SELECT statement in different ways is not the same thing!!!

Question

Let's take a look
use AdventureWorks2012
go
dbcc freeproccache
go
and now select something
select * from [HumanResources].[vEmployeeDepartmentHistory]
go
so, analyzing 'Compiled Plan'
SELECT usecounts, cacheobjtype, objtype, text
FROM Sys.dm_exec_cached_plans
CROSS APPLY sys.dm_exec_sql_text(plan_handle)
where cacheobjtype = 'Compiled Plan'
ORDER BY usecounts DESC;
GO
and now let's write some SELECT in "fuzzy case"
dbcc freeproccache
go
select * from [HUMANResources].[vEmployeeDepartmentHistory]
go
select * from [HumanRESOURCES].[vEmployeeDepartmentHistory]
go
select * from [HumanResources].[VEmployeeDepartmentHistory]
go
select * from [HumanResources].[vEmployeeDEPARTMENTHistory]
go
select * from [HumanResources].[vEmployeeDepartmentHISTORY]
go
SELECT * from [HumanResources].[vEmployeeDepartmentHistory]
go
select * FROM [HumanResources].[vEmployeeDepartmentHistory]
go
and now let's see compiled plans again
SELECT usecounts, cacheobjtype, objtype, text
FROM Sys.dm_exec_cached_plans
CROSS APPLY sys.dm_exec_sql_text(plan_handle)
where cacheobjtype = 'Compiled Plan'
ORDER BY usecounts DESC;
GO
So, write a SELECT statement in different ways is not the same thing!!!
Hope it'll be useful
P.Ceglie

Answer 1

Yes.  There is little or no query normalization that happens in front of the query plan cache.  It would be a performance tradeoff to parse and normalize the query before matching it to the cached plans.  The benefit of reducing the number
of plans in the cache probably wouldn't be worth it. 
David
David http://blogs.msdn.com/b/dbrowne/