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ISNUMERIC Trouble
From Wiki
If you use the ISNUMERIC function to determine if a value is numeric, you might be in for a surprise. Run the 3 lines of code below and you will see what I mean
- DECLARE @S VARCHAR(50)
- SET @S = CHAR(9) --- @S NOW CONTAINS THE TAB CHARACTER
- SELECT ISNUMERIC(@S), ISNUMERIC(CHAR(9)),ISNUMERIC('1D2'),ISNUMERIC('D')
As you can see, TAB is returned as numeric as well the value 1D2.
A better way to test for this would be with LIKE and %[a-z]%
If you run the example below you will see that the select statement with the ISNUMERIC function or LIKE returns one row more than the statement with LIKE and ISNUMERIC combined
- CREATE TABLE #foo (VALUE VARCHAR(20))
- INSERT INTO #foo
- SELECT '1' UNION ALL
- SELECT '3' UNION ALL
- SELECT 'B' UNION ALL
- SELECT '2' UNION ALL
- SELECT '33.331' UNION ALL
- SELECT 'adad1' UNION ALL
- SELECT '1d2' UNION ALL
- SELECT '^' UNION ALL
- SELECT '17777.999'
returns ^
- SELECT * FROM #foo
- WHERE VALUE NOT LIKE '%[a-z]%'
returns 1d2
- SELECT * FROM #foo
- WHERE ISNUMERIC(VALUE) = 1
returns correct result
- SELECT * FROM #foo
- WHERE VALUE NOT LIKE '%[a-z]%'
- AND ISNUMERIC(VALUE) = 1
Contributed by: --SQLDenis 03:17, 31 May 2008 (GMT)
Part of SQL Server Programming Hacks
Section Pitfalls
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