How can I query 'between' numeric data on a not numeric field?

Question

I\'ve got a query that I\'ve just found in the database that is failing causing a report to fall over. The basic gist of the query:

Select *
From table
Wher         


        

Answer 1

Use a CASE statement.

declare @StartRange int
declare @EndRange int

set @StartRange = 1
set @EndRange = 3

select *
from TestData
WHERE Case WHEN ISNUMERIC(Value) = 0 THEN 0
            WHEN Value IS NULL THEN 0
            WHEN Value = '' THEN 0
            WHEN CONVERT(int, Value) BETWEEN @StartRange AND @EndRange THEN 1
            END = 1

Answer 2

Not sure if this helps you, but I did read somewhere that incorrect conversion using CONVERT will always generate error in SQL. So I think it would be better to use CASE in where clause to avoid having CONVERT to run on all rows

Answer 3

IsNumeric only tells you that the string can be converted to one of the numeric types in SQL Server. It may be able to convert it to money, or to a float, but may not be able to convert it to an int.

Change your

IsNumeric(myField) = 1

to be:

not myField like '%[^0-9]%' and LEN(myField) < 9

(that is, you want myField to contain only digits, and fit in an int)

Edit examples:

select ISNUMERIC('.'),ISNUMERIC('£'),ISNUMERIC('1d9')

result:

----------- ----------- -----------
1           1           1

(1 row(s) affected)

Answer 4

You'd have to force SQL to evaluate the expressions in a certain order. Here is one solution

Select *
From ( TOP 2000000000
   Select *
   From table
   Where IsNumeric(myField) = 1
   And IsNull(myField, '') <> ''
   ORDER BY Key
) t0
Where Convert(int, myField) Between @StartRange And @EndRange

and another

Select *
From table
Where

CASE
   WHEN IsNumeric(myField) = 1 And IsNull(myField, '') <> ''
   THEN Convert(int, myField) ELSE @StartRange-1
END Between @StartRange And @EndRange

• The first technique is "intermediate materialisation": it forces a sort on a working table.
• The 2nd relies on CASE ORDER evaluation is guaranteed
• Neither is pretty or whizzy

SQL is declarative: you tell the optimiser what you want, not how to do it. The tricks above force things to be done in a certain order.