Question

I need to compare 2 tables to find a duplicate, but the fields allow duplicates.

For Example: 
Tbl1:
455
7991
7991

Tbl2: 
455
7991
7991
7991

I need to write a query that shows there is an extra 7991 in table 2. I tried a right join but it still finds the match so it doesn’t work properly. If anyone could point me in the right direction i’d greatly appreciate it. Thanks!!

Answer 1

SELECT  t1.colname
FROM    ( SELECT    colname
                  , COUNT(colname) AS colCount
          FROM      tbl1
          GROUP BY  colname
        ) t1
        INNER JOIN ( SELECT   colname
                      , COUNT(colname) AS colCount
               FROM     tbl2
               GROUP BY colname
             ) t2 ON t1.colname = t2.colname
                     AND t1.colCount <> t2.colCount