SQL query joins

Question

Hi everybody,
I have 4 tables A,B,C,D.
main_id is the primary column in all these tables and is used to join these tables. Table A has 600 records, B has 30 records, C has 1 record and D has 7 records.
When I join A and B, I get 36 records, A and C, I get 1 record, A and D I get 7 records.
But when I join A,B,C I get 36 records. For a regular join, this is correct, but my requirement is I need to get 36 records from A and B and also the one record from A and C. (reason for the one record not showing up is it is only pressent in A and C, not present in table B) I tried using outer joins, still doesn't serve the purpose. Tried union, but I need different columns from all the tables, and union supports only columns of same data type.
Could some SQL expert help me out?

Answer 1

Like this ?
SQL> create table a
  2  as
  3  select level main_id from dual connect by level <= 600
  4  /
Tabel is aangemaakt.
SQL> create table b
  2  as
  3  select level main_id, '*' column_b from dual connect by level <= 30
  4  /
Tabel is aangemaakt.
SQL> create table c
  2  as
  3  select 31 main_id, '^' column_c from dual
  4  /
Tabel is aangemaakt.
SQL> select a.main_id
  2       , b.column_b
  3       , c.column_c
  4    from a
  5       , b
  6       , c
  7   where a.main_id = b.main_id (+)
  8     and a.main_id = c.main_id (+)
  9     and (b.main_id is not null or c.main_id is not null)
10  /
   MAIN_ID C C
         1 *
         2 *
         3 *
         4 *
         5 *
         6 *
         7 *
         8 *
         9 *
        10 *
        11 *
        12 *
        13 *
        14 *
        15 *
        16 *
        17 *
        18 *
        19 *
        20 *
        21 *
        22 *
        23 *
        24 *
        25 *
        26 *
        27 *
        28 *
        29 *
        30 *
        31   ^
31 rijen zijn geselecteerd.Regards,
Rob.