Conversion failed when converting the varchar value to data type int.

Because [EntryTime] field is int and you are comparing it with 'December'

Make it like Month(EntryTime) =12 then it will work

How can I change Month(EntryTime)?

I would like to keep it as ='December'

Then you can do it like this

Datename (mm,[EntryTime]) ='December'

Does that work if I do this, using the < symbol

Datename (mm,[EntryTime]) <= 'December'

No, it will not wotk, Better you need to convert it into int and use it.
you can make a case statement if it is december then return 12 and can use it here.

Why do both of this statements produce different results?

select * from frmRegistrationCSW where Fiscal = 2013 and EntryTime <= '12/31/2012' and frmRegistrationCSWCheck11 = 1



select * from frmRegistrationCSW where Fiscal = 2013 and Datename (mm,[EntryTime]) <= 'December' and frmRegistrationCSWCheck11 = 1

Select allOpen in new window

I don't think that would make sense (because doing a character comparison).  Month(EntryTime)<=12 would normally make more sense except that generally that should always be true (I am unaware of any month being greater than 12 :-)).  Perhaps you would like to describe what it is you are trying to achieve?

Case statement?

Do you have an example?