db aggregation

tbl1:id  date--  --1   2012-02-011   2012-02-011   2012-02-011   2012-02-02tbl2:id  date--  --1   2012-02-021   2012-02-021   2012-02-021   2012-02-031   2012-02-031   2012-02-031   2012-02-03result:count_tbl1 count_tbl2  date--         --          --3          0            2012-02-011          3            2012-02-020          4            2012-02-03