Join two tables with a column with multiple entries for the other table

Question

I have the following problem. I want to join two tables.

The first table has entries like the following:

T1
PK    Info
1     one
2     two
3     three

The second table is build like this:

T2
PK    FKT1
1     1,3
2     1,2,3
3     2

My Result should show the following

PK2   FKT1   InfoT1
1     1,3    One,Three
2     1,2,3  One,two,Three
3     2      Two

I just cant get an idea how to solve this.

Is this possible only using sql selects or is a function needed?

kind regards

Never, ever store data as comma separated items. It will only cause you lots of trouble. — jarlh, Mar 01 '18 at 09:13
you can't store foreign keys in one column as comma separated — Yahya Mukhtar, Mar 01 '18 at 09:21

score 0 · Accepted Answer · answered Mar 01 '18 at 09:36

It's not that difficult, but - as you were told, you'd rather NOT do that.

SQL> with
  2  t1 (pk, info) as
  3    (select 1, 'one' from dual union
  4     select 2, 'two' from dual union
  5     select 3, 'three' from dual
  6    ),
  7  t2 (pk, fkt1) as
  8    (select 1, '1,3' from dual union
  9     select 2, '1,2,3' from dual union
 10     select 3, '2' from dual
 11    ),
 12  t2rows as
 13    (select pk, regexp_substr(fkt1, '[^,]+', 1, column_value) fkt1, column_value rn
 14     from t2,
 15          table(cast(multiset(select level from dual
 16                              connect by level <= regexp_count(fkt1, ',') + 1
 17                             ) as sys.odcinumberlist))
 18    )
 19  select t2r.pk,
 20    listagg(t2r.fkt1, ',') within group (order by t2r.rn) fkt1,
 21    listagg(t1.info, ',') within group (order by t2r.rn) infot1
 22  from t2rows t2r join t1 on t2r.fkt1 = t1.pk
 23  group by t2r.pk
 24  order by t2r.pk;

        PK FKT1                 INFOT1
---------- -------------------- --------------------
         1 1,3                  one,three
         2 1,2,3                one,two,three
         3 2                    two

SQL>

Join two tables with a column with multiple entries for the other table

1 Answers1