Question

I have the follow query:

  SELECT table1.data AS table1_data,
     table2.data AS table2_data,
     table3.data AS table3_data
    FROM table1, table2, table3
GROUP BY table1.data, table2.data, table3.data

which results:

table1_data  | table2_data  | table3_data
------------------------------------------
2012-11-15   | 2012-11-18   | 2012-11-20
2012-11-16   | 2012-11-18   | 2012-11-23
2012-11-17   | 2012-11-18   | 2012-11-27

when I expect:

all_tables_data
----------------
2012-11-15
2012-11-16
2012-11-17
2012-11-18
2012-11-18
2012-11-18
2012-11-20
2012-11-23
2012-11-27

I have “googled” some terms but I can’t describe this type of query, so, nothing found which can help solve the problem.

Answer 1

you should use “UNION ALL” instead of “GROUP BY”:

select table1.data from table1
union all
select table2.data from table2
union all
select table3.data from table3