Subquery referencing column in outer query

Question

I have a simplified problem such as...
select     a.year
,     (     select     b.column
          from     table b
          ,     (     select     c.year
                    from     table c
                    where     c.year = b.year  <= ORA-00904 "B"."YEAR": invalid identifier
          where     b.year = a.year
from     table a
group by a.yearMy question is why am I getting the error? Is there a way around it?

Answer 1

You cannot use a correlated sub-query in the from clause, only in the SELECT list or the WHERE clause.
Oracle does not see table b when resolving the in-line view in the from clause you need something more like:
SELECT a.year,     (SELECT column
                FROM (SELECT b.column
                      FROM table b,     
                           (SELECT c.year
                            FROM table c)
                      WHERE b.year = c.year)
                WHERE b.year = a.year)
FROM table a
GROUP BY a.year