Retrieving data from same table where multiple columns match in multiple rows

Question

I have a table with data where in a situation one rows' id becomes another rows reference id. The table is as below.

I tried to retrieve data as below,

select * from table1 t where t.id = t.reference_id

but it returns empty table.

Answer 1

Try a self join like :

select * from table1 t1
inner join table1 t2 on t1.id = t2.reference_id