CASE语句：将varchar值“不需要ed”转换为数据类型int时，转换失败

Question

I have a CASE statement in my code, I want to have a string on the ELSE '' END but get this error:

Conversion failed when converting the varchar value 'no ed is required' to data type int.

This is my code:

SELECT
    [Ticket ID],
    [Request Type],
    MAX(maxBuild),
    (CASE     
        WHEN [edBuild Date Documented] IS NOT NULL
             AND [edBuild Date Documented] > MAX(maxBuild)  
           THEN (DATEDIFF(DAY, [edBuild Date Documented], MAX(maxVal))) 
           ELSE '' 
     END) AS 'Days took from edBuild to validation/if 0 no edbuild involved'
FROM
    (SELECT DISTINCT
         CreatedDateTime AS [ticket submitted],
         IncidentID AS [Ticket ID],
         [titleT],
         (CASE     
             WHEN OwnedbyTeamT = 'xxx' 
                  AND ClosedDateTimeT <> '1899-12-30 00:00:00.000' 
                  AND TitleT LIKE '%ed%Build' 
                  AND (TitleT NOT LIKE '%Dup%') 
                THEN (ClosedDateTimeT) 
                ELSE 'no ed is required' 
          END) AS 'edBuild Date Documented'    
     FROM
         TaskView  
     WHERE
         IncidentID = '2272516 ' OR IncidentID = '2221' OR IncidentID = '21211') AS tt 
GROUP BY
    [Ticket ID], [Request Type],
    [MedBuild Date Documented],
    MAX(maxBuild)

is there any way to resolve this error?

Thanks

Answer 1

You can't mix the datatype .. if the result is varchar then cast the int to varchar too

THEN (CAST ClosedDateTimeT  AS VARCHAR) ELSE 'no ed is required' END) AS 'edBuild Date Documented'  

for

THEN cast( (DATEDIFF(DAY, [edBuild Date Documented], MAX(maxVal))) as VARCHAR)  ELSE '' ....

Answer 2

I suggest you to use NULL instead of '' . '' cannot be converted to int implicitly.

also if your result type is needed to be int you can use

SELECT CAST('' AS int);

result is 0