Order BY with ROWNUM in Select List

Question

Hi,
I have query like bellow for Oracle 11g:
create table em_c (vl_s_ec int,id_em_em int,id_empcre_ecr int, id_em_ec int);
create table em (id_em_em int)
Select e.id_em_em
, NVL(
(SELECT * FROM(SELECT a.vl_s_ec FROM em_c a WHERE a.id_em_em = ec.id_em_em
AND a.id_empcre_ecr < ec.id_em_ec order by a.id_em_ec DESC) WHERE ROWNUM <= 1) ,0) AS col2
FROM em_c ec
INNER JOIN em e on ec.id_em_em = e.id_em_em
WHERE 1 = 1;
But inner subselect doesn't see table "em_c ec" from outer FROM clause. That's why following error occurs:
SQL Error: ORA-00904: "EC"."ID_EM_EC": invalid identifier
Please help me to make it work.
Edited by: user11290901 on Dec 17, 2010 2:11 AM

Answer 1

Correlation names only go one level deep. It's a bit tough to decipher your query so if you want a better response please post the following:
1. Oracle version (SELECT * FROM V$VERSION)
2. Sample data in the form of CREATE / INSERT statements.
3. Expected output
4. Explanation of expected output (A.K.A. "business logic")
5. Use \ tags for #2 and #3. See FAQ (Link on top right side) for details.