How to fix this ORA-00918 error in this SQL code - sql

Question

I have ORA-00918 error with my code and i could not find the problem... the following code gives me this error.
ORA-00918 : column ambiguously defined
can anyone give me some advice? thanks
SELECT * FROM (
SELECT * FROM (
SELECT ROWNUM AS RNUM, A.XML_MSG_ID, A.LOGIN_ID, A.ORIGINATOR, A.RECIPIENT, A.ERROR_CODE, B.DOC_NO, B.DOC_NAME, B.ERROR_MSG
FROM XML_MANAGE_TBL A, XML_REFERENCE_TBL B
WHERE A.XML_MGS_ID = B.XML_MSG_ID
AND A.ERROR_CODE <> '00000000'
AND A.XML_MSG_ID >= '20190528' AND (SUBSTR(A.XML_MSG_ID, 1, 8)) <= '20190604' ) C, EBILL_USER D WHERE D.COMP_NUM = '1258169573' AND C.ORIGINATOR = D.ORIGINATOR )
WHERE RNUM BETWEEN CASE WHEN (1-1) != 0 THEN ((1-1)*50)+1 ELSE (1-1)*50 END
AND 1*50;

Answer 1

The problem is most probably in second subquery select *
SELECT * FROM (
... subquery C ...
) C, EBILL_USER D WHERE ... AND C.ORIGINATOR = D.ORIGINATOR
The table D contains the same columns as the subquery C, for sure the ORIGINATORcolumn
Simple change the second query to SELECT C.* and add only the required columns from D.
The general aproach how to troubleshoot ORA-00918 is to run the query from the innermost subquery and check that the returned column names are unique.
In your case try first, which should be fine
SELECT ROWNUM AS RNUM, A.XML_MSG_ID, A.LOGIN_ID, A.ORIGINATOR, A.RECIPIENT, A.ERROR_CODE, B.DOC_NO, B.DOC_NAME, B.ERROR_MSG
FROM XML_MANAGE_TBL A, XML_REFERENCE_TBL B
WHERE A.XML_MGS_ID = B.XML_MSG_ID
AND A.ERROR_CODE <> '00000000'
AND A.XML_MSG_ID >= '20190528' AND (SUBSTR(A.XML_MSG_ID, 1, 8)) <= '20190604'
Than run the second innermost subquery
SELECT * FROM (
SELECT ROWNUM AS RNUM, A.XML_MSG_ID, A.LOGIN_ID, A.ORIGINATOR, A.RECIPIENT, A.ERROR_CODE, B.DOC_NO, B.DOC_NAME, B.ERROR_MSG
FROM XML_MANAGE_TBL A, XML_REFERENCE_TBL B
WHERE A.XML_MGS_ID = B.XML_MSG_ID
AND A.ERROR_CODE <> '00000000'
AND A.XML_MSG_ID >= '20190528' AND (SUBSTR(A.XML_MSG_ID, 1, 8)) <= '20190604' ) C, EBILL_USER D WHERE D.COMP_NUM = '1258169573' AND C.ORIGINATOR = D.ORIGINATOR
In your IDE (e.g. SQL Developer) you will see one and more columns with a suffix _1 which is a sign of duplicated column that must be excluded (for columns from the equijoin predicate) or renamed.

Answer 2

you just need to remove outermost query and use C.RNUM instead of RNUM in where clause. Try with below code:
SELECT * FROM (
SELECT ROWNUM AS RNUM, A.XML_MSG_ID, A.LOGIN_ID, A.ORIGINATOR, A.RECIPIENT, A.ERROR_CODE, B.DOC_NO, B.DOC_NAME, B.ERROR_MSG
FROM XML_MANAGE_TBL A, XML_REFERENCE_TBL B
WHERE A.XML_MGS_ID = B.XML_MSG_ID
AND A.ERROR_CODE <> '00000000'
AND A.XML_MSG_ID >= '20190528' AND (SUBSTR(A.XML_MSG_ID, 1, 8)) <= '20190604' ) C, EBILL_USER D WHERE D.COMP_NUM = '1258169573' AND C.ORIGINATOR = D.ORIGINATOR
and (C.RNUM BETWEEN CASE WHEN (1-1) != 0 THEN ((1-1)*50)+1 ELSE (1-1)*50 END AND 1*50);