Question

I have this sql:

SELECT
    sa.answertext
FROM dbo.tblsurveyanswer sa
            INNER JOIN dbo.tblsurvey s
                ON s.surveyid = sa.surveyid
            INNER JOIN dbo.tblquestion q
                ON q.questionid = sa.questionid
            INNER JOIN dbo.tblshqscriteria c
                ON c.shqscriteriaid = q.shqscriteriaid
            INNER JOIN dbo.tblshqsdescription d
                ON d.shqsdescriptionid = q.shqsdescriptionid
            INNER JOIN dbo.tblrepairpercentage rp
                ON rp.repairpercentageid = sa.repairpercentageid
WHERE 
(c.shqscriteria = 'qwerty')
OR 
(c.shqscriteria = 'zxcvb' AND ISNUMERIC(sa.answertext) = 1 AND CAST(sa.answertext AS float) < 5)

First time I execute it fails with “Error converting data type varchar to float.”
Second time* I execute it succeeds – returning no rows because there are no ‘qwerty’ or ‘zxcvb’ shqscriteria

*actually sometimes I have to hit execute up to 8 times before I get the failure

Answer 1

As long as you’re not using aggregates, you should be able to rely on CASE’s order of execution:

WHERE
...
OR
(
  c.shqscriteria = 'zxcvb' 
  AND 5 > CASE WHEN ISNUMERIC(sa.answertext) = 1      
    THEN CAST(sa.answertext AS float) 
    ELSE 6 
  END
)

Note however that ISNUMERIC(col) = 1 does not always mean that col is eligible to be converted to a specific numeric type.