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Count Decimal Places


Count Decimal Places

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Keith Saynor
Keith Saynor
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i'm trying to count the number of decimal places in a field.

e.g. mynumber decimal 9 (18,9)

Len(mynumber) result = 11

I've tried converting it to a string Len(STR(mynumber)) result = 10

What I really want is a count of the number of digits following the decimal point ignoring the trailing zeros

e.g. 0.8333 result should be 4

0.99 result should be 2

Any ideas - Thanks





Ken McKelvey
Ken McKelvey
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DECLARE @D DECIMAL(18,9)
,@S VARCHAR(20)
,@R VARCHAR(20)

SET @D = 0.8333
SET @S = CAST(@D AS VARCHAR(20))
SET @R = REVERSE(SUBSTRING(@S, CHARINDEX('.', @S) + 1, 20))

SELECT LEN(SUBSTRING(@R, PATINDEX('%[1-9]%', @R), 20))


Ken McKelvey
Ken McKelvey
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Forgot about no Decimal places:

DECLARE @D DECIMAL(18,9)
,@S VARCHAR(20)
,@R VARCHAR(20)
,@Pos SMALLINT

SET @D = 0.0
SET @S = CAST(@D AS VARCHAR(20))
SET @R = REVERSE(SUBSTRING(@S, CHARINDEX('.', @S) + 1, 20))
SET @Pos = PATINDEX('%[1-9]%' , @R)
IF @Pos = 0
SELECT 0
ELSE
SELECT LEN(SUBSTRING(@R, @Pos, 20))


R Michael
R Michael
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For what it's worth, here is a set-based approach. It requires a numbers table though.



IF EXISTS ( SELECT 1
FROM dbo.sysobjects
WHERE id = OBJECT_ID(N'[dbo].[CountDP]')
AND xtype IN ( N'FN', N'IF', N'TF' ) )
BEGIN
DROP FUNCTION [dbo].[CountDP]
END
GO

CREATE FUNCTION [dbo].[CountDP]
(
@decNumber DECIMAL(18, 9)
)
RETURNS TINYINT
AS BEGIN
/*******************************************************************************************************
* dbo.CountDP
*
* Usage:
print dbo.countdp(10.0000001) -- 7
print dbo.countdp(10) -- 0
print dbo.countdp(10.000) -- 0
print dbo.countdp(0) -- 0
print dbo.countdp(0.1234567) -- 7
print dbo.countdp(null) -- null
print dbo.countdp() --ERROR

*
* Modifications:
* Developer Name Date Brief description
* ------------------- ----------- ------------------------------------------------------------
*
********************************************************************************************************/

DECLARE @DecCount TINYINT

SELECT @DecCount = ( SELECT ISNULL(MAX(num), N.Num)
FROM Numbers
WHERE Num < 18
AND Num > N.Num
AND SUBSTRING(CAST(@decNumber AS VARCHAR),
Num, 1) NOT IN ( '0', '' )
) - ( Num )
FROM Numbers N
WHERE Num < LEN(CAST(@decNumber AS VARCHAR(18)))
AND SUBSTRING(CAST(@decNumber AS VARCHAR), Num, 1) = '.'
RETURN @DecCount

END
GO


SQL guy and Houston Magician
Sergiy
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This function is about 100 times faster:

IF EXISTS (SELECT * FROM sysobjects WHERE name = N'DecimalPlaces')
DROP FUNCTION DecimalPlaces
GO

CREATE FUNCTION dbo.DecimalPlaces
(@A float)
RETURNS tinyint
AS
BEGIN
declare @R tinyint

IF @A IS NULL
RETURN NULL

set @R = 0

while @A - str(@A, 18 + @R, @r) <> 0
begin
SET @R = @R + 1
end

RETURN @R
END
GO


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No, it's actually much worse.

I tested my function against 16540 row table.
It returned result in 3..5 seconds (I'm not alone on that server )

Than I started same query but using function [dbo].[CountDP].
I's been 2 hours 50 minutes since then, it's still going.

So, there is a reminder: avoid referencing tables inside UDF!
Even if it's such "set based" table as Numbers.


Jeff Moden
Jeff Moden
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Old guys rule... 1 million conversions... 11 seconds... works for positive numbers, negative numbers, zero, and NULL...

DECLARE @Places INT
SELECT TOP 1000000 @Places = FLOOR(LOG10(REVERSE(ABS(SomeNumber)+1)))+1
FROM dbo.BigTest



--Jeff Moden

RBAR is pronounced ree-bar and is a Modenism for Row-By-Agonizing-Row.
First step towards the paradigm shift of writing Set Based code:
Stop thinking about what you want to do to a row... think, instead, of what you want to do to a column.
If you think its expensive to hire a professional to do the job, wait until you hire an amateur. -- Red Adair

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R Michael
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Ouch! I guess next time I should get more information on how a solution might be used before posting a response!

Interesting solutions all around, I thought. Very slick guys!

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Vladan
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Jeff,

are you sure the code you posted works? I tried it out of curiosity, and I'm getting some strange results... e.g. for number 99, depending on how I enter it, result is either 1 or -2.

DECLARE @Places INT
SELECT @Places = FLOOR(LOG10(REVERSE(ABS(cast (99 as float))+1)))+1
SELECT @places
-----------
1

(1 row(s) affected)

DECLARE @Places INT
SELECT @Places = FLOOR(LOG10(REVERSE(ABS(99.0000)+1)))+1
SELECT @places
-----------
-2

(1 row(s) affected)





Jeff Moden
Jeff Moden
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There would certainly appear to be a fly in the ointment ... thanks for the catch and sorry for the mistake folks... I'll see if I can fix it... Maybe I meant "Old guys drool"

--Jeff Moden

RBAR is pronounced ree-bar and is a Modenism for Row-By-Agonizing-Row.
First step towards the paradigm shift of writing Set Based code:
Stop thinking about what you want to do to a row... think, instead, of what you want to do to a column.
If you think its expensive to hire a professional to do the job, wait until you hire an amateur. -- Red Adair

Helpful Links:
How to post code problems
How to post performance problems
Forum FAQs
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