Michael Valentine Jones (9/27/2013)

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Jeff Moden (9/26/2013)

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Michael Valentine Jones (9/26/2013)

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Jeff Moden (9/26/2013)

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Michael Valentine Jones (9/25/2013)

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That's not really the best way to go because it depends on the setting of a run-time session parameter, DATEFIRST.

Although I certainly prefer you method, I have to ask... why does everyone have such a problem with that? It's no different than setting a variable that would be used as a constant. The only time that such a setting change would be a problem is if it were in a function, which can't be done TTBOMK.

I wanted the OP to be aware of the limitations of their method. They are certainly free to ignore my wonderful advice. 😎

I prefer to have code that works as expected under the widest possible conditions, especially if it's no harder to code.

People may be operating with different default languages than our "normal" US English, and that can change the setting of DATEFIRST, and the client application can also define that setting in an unexpected way.

Absolutely agreed across all points especially the part about it not being any more difficult. I was actually talking about putting SET DATEFIRST into the actual code, though. If someone can't figure out the integer math, I can't see why you couldn't use SET DATEFIRST for the session. People seem almost phobic about its use.

If you set DATEFIRST to something other than the expected value, there could be downstream issues in the next procedure or code that gets executed if it depends on the setting of DATEFIRST. Or if your code depends on the setting of DATEFIRST, you don't specifically set DATEFIRST, and upstream code has modified DATEFIRST to an unexpected value.

If you are going to use DATEFIRST, it is probably best to set it specifically and then reset it to the default if you are setting it to a non-default value.

If you are using connection pooling, I believe that the value of DATEFIRST does get reset to the default by the API stored procedure sp_reset_connection (unlike the isolation level :angry: )

set nocount on

set datefirst 7 -- Normal US English setting

select DW1 = datepart(dw,'20130927')

go

set datefirst 3 -- Set to Wednesday

select DW2 = datepart(dw,'20130927')

go

exec ('select DW3 = datepart(dw,''20130927'')')

Results:

DW1

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6

DW2

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3

DW3

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3