Case statement that adds column values

Question

I need to write a case statement that will return

"1 of 3" if someone voted in one of three elections, 
"2 of 3" if someone voted in two of three elections, 
"3 of 3" if someone voted in three of three elections, 

The problem is that some of the values ​​are varchar and some are null, and I cannot add them. This is my idea, but I cannot get it to work.

select 
id,
CASE 
     WHEN race1 + race2 + race3 = 0 then '0-3'
     WHEN race1 + race2 + race3 = 1 then '1-3'
     WHEN race1 + race2 + race3 = 2 then '2-3'
     WHEN race1 + race2 + race3 = 3 then '3-3'
     WHEN race1 + race2 + race3 is null then 'Unknown'
 END AS General_Turnout
from test4

http://sqlfiddle.com/#!3/cac66/3

Answer 1

This should work:

select 
id,
    CAST( (CASE WHEN race1 IS NOT NULL THEN 1 ELSE 0 END)
   +(CASE WHEN race2 IS NOT NULL THEN 1 ELSE 0 END)
   +(CASE WHEN race3 IS NOT NULL THEN 1 ELSE 0 END) AS CHAR) + '-3'
AS General_Turnout
from test4

Answer 2

use COELESCE (value, 0) so that zero is taken as zero

Answer 3

, SQLfiddle, , NULL , , . , race1, race2 race3, :

SELECT 
  id,
  CAST(
    CASE WHEN race1 IS NOT NULL then 1 ELSE 0 END +
    CASE WHEN race2 IS NOT NULL then 1 ELSE 0 END +
    CASE WHEN race3 IS NOT NULL then 1 ELSE 0 END
  AS CHAR) + '-3' AS General_Turnout
FROM test4