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Is my function nondeterministic one
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onefunctionnondeterministic
Problem
I have two functions: fn_Without_Param and fn_With_Param
and
In the first case I have nondeterministic (?) function (because of GETUTCDATE) and I have called the second one with the same input parameter (CONVERT( varchar(10), GETUTCDATE(), 101 ) - meens today date without hours, minutes, seconds, millisecond).
Is my function nondeterministic one? How to detect this, maybe sql server has some public mark. Why is the second function slower?
CREATE FUNCTION [dbo].[fn_Without_Param]
(
)
...
INNER JOIN .. ON .. AND SubmitDate = CONVERT( varchar(10), GETUTCDATE(), 101 )and
/*
I am requesting it so:
declare @SubmitDate datetime
set @SubmitDate = CONVERT( varchar(10), GETUTCDATE(), 101 )
select * from [dbo].[fn_With_Param] (@SubmitDate)
*/
CREATE FUNCTION [dbo].[fn_With_Param]
(
@SubmitDate datetime
)
...
INNER JOIN .. ON .. AND SubmitDate = @SubmitDateIn the first case I have nondeterministic (?) function (because of GETUTCDATE) and I have called the second one with the same input parameter (CONVERT( varchar(10), GETUTCDATE(), 101 ) - meens today date without hours, minutes, seconds, millisecond).
Is my function nondeterministic one? How to detect this, maybe sql server has some public mark. Why is the second function slower?
Solution
I'm not sure if there is a flag, but there is a reference available at http://msdn.microsoft.com/en-us/library/ms178091.aspx of which built in functions are deterministic.
GETDATE() and GETUTCDATE() are nondeterministic because if you call them multiple times with the same parameters, which in this case are none, you get different values. In other words, the return value is not determined by input.
As far as why the second is slower than the first, check for implicit conversion between SubmitDate = @SubmitDate. Are they both datetime?
GETDATE() and GETUTCDATE() are nondeterministic because if you call them multiple times with the same parameters, which in this case are none, you get different values. In other words, the return value is not determined by input.
As far as why the second is slower than the first, check for implicit conversion between SubmitDate = @SubmitDate. Are they both datetime?
Context
StackExchange Database Administrators Q#726, answer score: 9
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