my $sql = " SELECT * 
              FROM
                 ( SELECT name, city, COUNT(*) AS Rows 
                  FROM file.csv
                  WHERE ( mydate >= ? ) 
                  AND  ( mydate   < ? ) ) t1 
              INNER JOIN
                 ( SELECT name, city, COUNT(*) AS Rows 
                   FROM file.csv 
                   WHERE ( mydate >= ? )
                  AND ( mydate < ? ) ) t2 
              ON t1.mydate = t2.mydate";