mysql - Join on matching records and create combinations when no match -

i trying create new table using 2 others. want create record combinations of records while merging 'value' column. want column tells me value this.:

a:

day    month   random1    random2    value1  01     jan     aa         xx         12      24     mar     bb         yy         34      13     feb     cc         zz         7 

b:

day    month   value2 03     jan     16 24     mar     2 

i trying join them on day , month, want create row combinations if there no row match.

i want table follows:

c:

day    month   random1    random2    value    type 01     jan     aa         xx         12       value1 24     mar     bb         yy         34       value1 13     feb     cc         zz         7        value1 03     jan     aa         xx         16       value2 03     jan     aa         yy         16       value2 03     jan     aa         zz         16       value2 03     jan     bb         xx         16       value2 03     jan     bb         yy         16       value2 03     jan     bb         zz         16       value2 03     jan     cc         xx         16       value2 03     jan     cc         yy         16       value2 03     jan     cc         zz         16       value2 24     mar     aa         xx         2        value2 24     mar     aa         yy         2        value2 24     mar     aa         zz         2        value2 24     mar     bb         xx         2        value2 24     mar     bb         yy         2        value2 24     mar     bb         zz         2        value2 24     mar     cc         xx         2        value2 24     mar     cc         yy         2        value2 24     mar     cc         zz         2        value2 

my sql query unusually complicated , sure there simple way of doing this. (i writing query in r using sqldf(), looking sql suggestion open alternatives.)

it appears though result set includes set a, plus set combination of unique values of random1, unique values of random2 , set b.

i use this

select day, month, random1, random2, value1, 'value1' type tablea union select tableb.day, tableb.month, r1.random1, r1.random2, tableb.value2, 'value2' tableb join (select distinct random1       tablea) r1 join (select distinct random2       tablea) r2;