Try this version using a Tally table. No loops, no cursors.

IF OBJECT_ID ( 'tempdb..#Tally' ) IS NOT NULL

BEGIN

DROP TABLE #Tally

END

GO

DECLARE @AlphaNumber varchar ( 20 )

DEcLARE @numtoadd decimal ( 20, 4 )

DECLARE @NumPart decimal ( 20, 4 )

DECLARE @Result varchar ( 20 )

DECLARE @strlen int

DECLARE @numpos int

SET @AlphaNumber = 'ABC12345.6789'

SET @numtoadd = 0.3211

SET @strlen = DATALENGTH ( @AlphaNumber )

SELECT TOP ( @strlen )

IDENTITY ( int, 1, 1 ) AS N

INTO #Tally

FROM master.dbo.syscolumns

ALTER TABLE #Tally

ADD C char ( 1 )

UPDATE #Tally SET C = SUBSTRING ( @AlphaNumber, N, 1 )

--SELECT * FROM #Tally

SELECT @numpos = MIN ( N ) FROM #Tally WHERE C BETWEEN '0' AND '9' OR C = '.'

--PRINT @numpos

SET @NumPart = CAST ( SUBSTRING ( @AlphaNumber, @numpos, @strlen ) AS decimal ( 20, 4 ) )

--PRINT @NumPart

SET @NumPart = @NumPart + @numtoadd

SET @Result = LEFT ( @AlphaNumber, @numpos - 1 ) + LTRIM ( STR ( @NumPart, @strlen, 4 ) )

PRINT @AlphaNumber + ' + ' + LTRIM ( STR ( @numtoadd, 10, 4 ) ) + ' = ' + @Result

DROP TABLE #Tally

I know, it breaks if there is no numeric part or there is more than one decimal point 🙂

Regards,

Jan