Count distinct values on sevaral fields 1

SELECT daCode
     , COUNT(*) AS daCount
  FROM ( SELECT Code1 AS daCode
           FROM daTable
          WHERE Code1 IS NOT NULL
         UNION ALL
         SELECT Code2 
           FROM daTable
          WHERE Code2 IS NOT NULL
         UNION ALL
         SELECT Code3 
           FROM daTable
          WHERE Code3 IS NOT NULL
         UNION ALL
         SELECT Code4 
           FROM daTable
          WHERE Code4 IS NOT NULL
       ) AS d
GROUP
    BY daCode

select Work.Code, count(*) from (
select Code1 as Code from table1
union all
select Code2 as Code from table1
) as Work
where Work.Code is not null
group by Work.Code