In tbl_1 I have:
id
1
2
3
4
5
6
7
8
9
in tbl_2:
id value
1 1,2,3
2 5
Select * from tbl_1 where id in (Select value from tbl_2 where id = 2); --is OK
Select * from tbl_1 where id in (Select value from tbl_2 where id = 1);
--Need this resault: 3 rows: 1, 2 and 3
Fix your data model! You should not be storing numbers as strings. You should have properly declared foreign key relationships. Strings should not be used to store multiple values.
Sometimes, we are stuck with other people's really, really, really bad decisions. You can do what you want with `like:
Select t1.*
from tbl_1 t1
where exists (select 1
from tbl_2 t2
where t2.id = 1 and
',' || t2.value || ',' like '%,' || t1.id ',%'
);
However, your effort should be going into fixing the data, rather than trying to deal with it. The correct data would be a junction/association table with one row per id and value for table 2:
id value
1 1
1 2
1 3
2 5
Yet another option:
SQL> with
2 -- sample data
3 tbl_1 (id) as
4 (select 1 from dual union all
5 select 2 from dual union all
6 select 3 from dual union all
7 select 4 from dual union all
8 select 5 from dual union all
9 select 6 from dual union all
10 select 7 from dual union all
11 select 8 from dual union all
12 select 9 from dual
13 ),
14 tbl_2 (id, value) as
15 (select 1, '1,2,3' from dual union all
16 select 2, '5,6,7' from dual
17 )
18 -- query which returns what you want
19 select a.id
20 from tbl_1 a join
21 (select regexp_substr(b.value, '[^,]+', 1, column_value) id
22 from tbl_2 b cross join
23 table(cast(multiset(select level from dual
24 connect by level <= regexp_count(b.value, ',') + 1
25 ) as sys.odcinumberlist))
26 where b.id = 1
27 ) c on c.id = a.id;
ID
----------
1
2
3
SQL>
One option uses string functions:
select t1.*
from t1
inner join t2 on ',' || t2.value || ',' like '%,' || t1.id || ',%'
where t2.id = 1
