Adding a CASE statement has dramatically increased my query execution time

Question

I have added the following CASE statement in my query:

CASE starlingYear
    WHEN  CONVERT(VARCHAR, 3000) THEN 'Not yet active'
ELSE CONVERT(VARCHAR, starlingYear)
END AS starBirth

Adding this CASE has increased the query execution time from less than a second to about 8 or 10 seconds.

The query only has about 1000 rows.

Is there a way to increase performance?

Answer 1

The syntax should be as follows. If startlingYear is 3000 (int) then 'Not yet active' else convert starlingYear to varchar.

SELECT CASE  starlingYear
    WHEN 3000 
       THEN 'Not yet active'
    ELSE 
       CONVERT(VARCHAR(30), starlingYear) 
    END AS starBirth
FROM table1