Ok... this takes 2 seconds longer (1,000,000 rows in 23 seconds instead of 21)... had to work around the "zero domain" on the LOG10 function to get this to work properly for whole numbers...

DECLARE @TestNum DECIMAL(38,15)
    SET @TestNum = 99   --99.0000

 SELECT CASE
            WHEN FLOOR(REVERSE(ABS(@TestNum))) = 0.0
            THEN 0
            ELSE FLOOR(LOG10(REVERSE(ABS(@TestNum)))+1)
        END

It does NOT support FLOAT... (the original problem description was based on the DECIMAL datatype so I think we're ok there)... Float does wierd things when you throw a REVERSE on it.  If anyone needs a decimal place counter that works on FLOAT, we'll have to take a different tact...

10-PATINDEX('%[^0]%',REVERSE(RIGHT(CAST(mynumber as varchar),9))+'1')

1,000,000 rows <=10 secs

Far away is close at hand in the images of elsewhere.

Anon.

Very cool, David... fast as all get out... but try this... obviously, we have to know exactly what the scale of the decimal places is to use it or we come up with the wrong answer...

DECLARE @TestNum DECIMAL(38,15)
    SET @TestNum = 99.123456789012345
 SELECT 10-PATINDEX('%[^0]%',REVERSE(RIGHT(CAST(@TestNum as varchar),9))+'1')

However... you gave me one heck of an idea... the following takes a bit more time (1,000,000 records in about 12 seconds)...

DECLARE @TestNum DECIMAL(38,15)
    SET @TestNum = 90 --99.123456780000000 --0.123456780000000 --99.1 --90

SELECT CHARINDEX('.',REVERSE(@TestNum))
      -PATINDEX('%[^0]%',REVERSE(@TestNum))

...the neat thing about it is that you don't need to know the precision or scale of the decimal column... it figures it out...

 SELECT TestNum, Jeff=CASE
            WHEN FLOOR(REVERSE(ABS(TestNum))) = 0.0
            THEN 0
            ELSE FLOOR(LOG10(REVERSE(ABS(TestNum)))+1) END
        ,Markus=CASE 
            WHEN FLOOR(LOG10(REVERSE(ABS(TestNum)+1)))+1 < 0 
            THEN 0 ELSE FLOOR(LOG10(REVERSE(ABS(TestNum)+1)))+1 END
        ,Dwain=CASE
            WHEN FLOOR(TestNum) = TestNum THEN 0
            ELSE LEN(CAST(REVERSE(ABS(TestNum) % 1) AS DECIMAL(38,0))) END
FROM (
    SELECT CAST(99 AS DECIMAL(38,15))
    UNION ALL SELECT CAST(99.1 AS DECIMAL(38,15))
    UNION ALL SELECT CAST(99.11 AS DECIMAL(38,15))
    UNION ALL SELECT CAST(99.111 AS DECIMAL(38,15))
    UNION ALL SELECT CAST(99.1111 AS DECIMAL(38,15))
    UNION ALL SELECT CAST(99.11111 AS DECIMAL(38,15))
    UNION ALL SELECT CAST(99.111111 AS DECIMAL(38,15))
    UNION ALL SELECT CAST(99.1111111111111111 AS DECIMAL(38,15))
    UNION ALL SELECT CAST(0.1 AS DECIMAL(38,15))) Nums(TestNum)

CREATE TABLE #BigNums (TestNum DECIMAL(38,15))

INSERT INTO #BigNums
SELECT 1.* CHECKSUM(NEWID()) / POWER(10, ABS(CHECKSUM(NEWID())) % 10)
FROM (
    SELECT TOP 1000000 1
    FROM sys.all_columns a, sys.all_columns b
    )Tally(n)

DECLARE @Hold DECIMAL(38,15)

PRINT 'Jeff'
SET STATISTICS TIME ON
 SELECT @Hold=CASE
            WHEN FLOOR(REVERSE(ABS(TestNum))) = 0.0
            THEN 0
            ELSE FLOOR(LOG10(REVERSE(ABS(TestNum)))+1)
        END
FROM #BigNums
SET STATISTICS TIME OFF

PRINT 'Markus'
SET STATISTICS TIME ON
 SELECT @Hold=CASE 
            WHEN FLOOR(LOG10(REVERSE(ABS(TestNum)+1)))+1 < 0 
            THEN 0 ELSE FLOOR(LOG10(REVERSE(ABS(TestNum)+1)))+1 END
FROM #BigNums
SET STATISTICS TIME OFF

PRINT 'Dwain'
SET STATISTICS TIME ON
 SELECT @Hold=CASE
        WHEN FLOOR(TestNum) = TestNum THEN 0
        ELSE LEN(CAST(REVERSE(ABS(TestNum) % 1) AS DECIMAL(38,0))) END
FROM #BigNums
SET STATISTICS TIME OFF

DROP TABLE #BigNums

Jeff

 SQL Server Execution Times:
   CPU time = 3339 ms,  elapsed time = 3411 ms.

Markus

 SQL Server Execution Times:
   CPU time = 4227 ms,  elapsed time = 4291 ms.

Dwain

 SQL Server Execution Times:
   CPU time = 2028 ms,  elapsed time = 2036 ms.

 SELECT TestNum, Jeff=CASE
            WHEN FLOOR(REVERSE(ABS(TestNum))) = 0.0
            THEN 0
            ELSE FLOOR(LOG10(REVERSE(ABS(TestNum)))+1) END
        ,Markus=CASE 
            WHEN FLOOR(LOG10(REVERSE(ABS(TestNum)+1)))+1 < 0 
            THEN 0 ELSE FLOOR(LOG10(REVERSE(ABS(TestNum)+1)))+1 END
        ,Dwain=CASE
            WHEN FLOOR(TestNum) = TestNum THEN 0
            ELSE LEN(CAST(REVERSE(ABS(TestNum) % 1) AS DECIMAL(38,0))) END
        ,DwainRedux=CASE
            WHEN FLOOR(TestNum) = TestNum THEN 0
            ELSE LEN(CAST(REVERSE(TestNum - CAST(FLOOR(TestNum) AS DECIMAL)) AS DECIMAL)) END
FROM (
    SELECT CAST(99 AS DECIMAL(38,15))
    UNION ALL SELECT CAST(99.1 AS DECIMAL(38,15))
    UNION ALL SELECT CAST(99.11 AS DECIMAL(38,15))
    UNION ALL SELECT CAST(99.111 AS DECIMAL(38,15))
    UNION ALL SELECT CAST(99.1111 AS DECIMAL(38,15))
    UNION ALL SELECT CAST(99.11111 AS DECIMAL(38,15))
    UNION ALL SELECT CAST(99.111111 AS DECIMAL(38,15))
    UNION ALL SELECT CAST(-99.11111 AS DECIMAL(38,15))
    UNION ALL SELECT CAST(-99.111111 AS DECIMAL(38,15))
    UNION ALL SELECT CAST(99.1111111111111111 AS DECIMAL(38,15))
    UNION ALL SELECT CAST(0.1 AS DECIMAL(38,15))) Nums(TestNum)

CREATE TABLE #BigNums (TestNum DECIMAL(38,15))

INSERT INTO #BigNums
SELECT 1.* CHECKSUM(NEWID()) / POWER(10, ABS(CHECKSUM(NEWID())) % 10)
FROM (
    SELECT TOP 1000000 1
    FROM sys.all_columns a, sys.all_columns b
    )Tally(n)

DECLARE @Hold DECIMAL(38,15)

PRINT 'Jeff'
SET STATISTICS TIME ON
 SELECT @Hold=CASE
            WHEN FLOOR(REVERSE(ABS(TestNum))) = 0.0
            THEN 0
            ELSE FLOOR(LOG10(REVERSE(ABS(TestNum)))+1)
        END
FROM #BigNums
SET STATISTICS TIME OFF

PRINT 'Markus'
SET STATISTICS TIME ON
 SELECT @Hold=CASE 
            WHEN FLOOR(LOG10(REVERSE(ABS(TestNum)+1)))+1 < 0 
            THEN 0 ELSE FLOOR(LOG10(REVERSE(ABS(TestNum)+1)))+1 END
FROM #BigNums
SET STATISTICS TIME OFF

PRINT 'Dwain'
SET STATISTICS TIME ON
 SELECT @Hold=CASE
        WHEN FLOOR(TestNum) = TestNum THEN 0
        ELSE LEN(CAST(REVERSE(ABS(TestNum) % 1) AS DECIMAL(38,0))) END
FROM #BigNums
SET STATISTICS TIME OFF

PRINT 'Dwain Redux'
SET STATISTICS TIME ON
 SELECT @Hold=CASE 
        WHEN FLOOR(TestNum) = TestNum THEN 0
        ELSE LEN(CAST(REVERSE(TestNum - CAST(FLOOR(TestNum) AS DECIMAL)) AS DECIMAL)) END
FROM #BigNums
SET STATISTICS TIME OFF

PRINT 'Jeff - Revised WHEN'
SET STATISTICS TIME ON
 SELECT @Hold=CASE
            WHEN FLOOR(TestNum) = TestNum 
            THEN 0
            ELSE FLOOR(LOG10(REVERSE(ABS(TestNum)))+1)
        END
FROM #BigNums
SET STATISTICS TIME OFF

DROP TABLE #BigNums

Jeff

 SQL Server Execution Times:
   CPU time = 3338 ms,  elapsed time = 3408 ms.

Markus

 SQL Server Execution Times:
   CPU time = 4337 ms,  elapsed time = 4369 ms.

Dwain

 SQL Server Execution Times:
   CPU time = 2012 ms,  elapsed time = 2071 ms.

Dwain Redux

 SQL Server Execution Times:
   CPU time = 1888 ms,  elapsed time = 1928 ms.

Jeff - Revised WHEN

 SQL Server Execution Times:
   CPU time = 2293 ms,  elapsed time = 2362 ms.