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 Power(n,n) result VS Windows Calculator		  Reply to Topic
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neo_bagsjol
Starting Member

6 Posts
Posted - 03/05/2014 :  21:56:52  Show Profile  Reply with Quote
Hello guys

i would like to ask why the result from Power function of sqlserver is different from the windows calculator for example

SQL RESULT

SELECT POWER('1.0116666666666667','120')

RESULT IS: 4.02247064115812

WINDOWS CALCULATOR
1.0116666666666667 ^ 120

RESULT IS:4.0224706411581114419518589580497

Is there a way to compute result like windows calc from sqlserver coz
i'm having different result when i run my script using Power function at the end of result i got -0.01 instead of 0.00

i need your help please i been doing this for 2 weeks still i got negative result

thanks guys

maunishq
Yak Posting Veteran

Canada
71 Posts
Posted - 03/06/2014 :  11:04:29  Show Profile  Reply with Quote
Can you edit your script? If yes, then limit the power portion to the same number of decimals SQL is showing. e.g CAST ... AS NUMERIC(20,14)

=======================
Not an Expert, Just a learner.
!_(M)_!
Edited by - maunishq on 03/06/2014 11:04:58
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Lamprey
Flowing Fount of Yak Knowledge

4614 Posts
Posted - 03/06/2014 :  11:26:39  Show Profile  Reply with Quote
I don't think there is much you can do other than write your own Power function. The built-in function uses a float. Since that is an approximate data type, you won't get very precise results.
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Lamprey
Flowing Fount of Yak Knowledge

4614 Posts
Posted - 03/06/2014 :  11:33:55  Show Profile  Reply with Quote
I was just curious so I wrote a quick loop to see what the results would be. Due to the way SQL Server handles Decimal/Numeric multiplication you need to set the scale really high to get a precise result:
DECLARE @Val DECIMAL(38, 37) = 1.0116666666666667;
DECLARE @Exponent INT = 120;
DECLARE @Result DECIMAL(38, 37);

WHILE @Exponent - 1 > 0
BEGIN
	SET	@Result = 
		CASE 
			WHEN @Result IS NULL THEN @Val * @Val
			ELSE @Result * @Val
		END
	SET @Exponent = @Exponent - 1
END

SELECT @Result

RESULT: 4.0224706411581114419518589580496877300
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