ORA-00904 in Merge statement

Question

I encountered with ORA-00904 in Merge statement. I fixed the error but I don't know why. Would you please help me explain it? Thanks in advance. The following is the detail description of my question.
I have two tables TBL_A<col1 integer,col2 integer> TBL_B<col1 integer,col2 integer> and an anonymous block to test executed in Oracle 10gR2.
DECLARE
V_NUM INTEGER;
BEGIN
V_NUM := 1;
/*merge I it's okay.the function of merge seems meaningless, please pay attention to its grammar*/
MERGE INTO TBL_A A
USING (SELECT V_NUM N, COL1, COL2 FROM TBL_B) B
ON (A.COL1 = B.N)
WHEN MATCHED THEN
UPDATE SET A.COL2 = B.COL2;
/*merge II*/
/*ora-00904*/
MERGE INTO TBL_A A
USING (SELECT V_NUM, COL1, COL2 FROM TBL_B) B
ON (A.COL1 = V_NUM)
WHEN MATCHED THEN
UPDATE
SET A.COL2 = B.COL2;
/*merge III is okay*/
MERGE INTO TBL_A A
USING (SELECT COL1, COL2 FROM TBL_B) B
ON (A.COL1 = V_NUM)
WHEN MATCHED THEN
UPDATE
SET A.COL2 = B.COL2;
COMMIT;
END;
I traced the 904 error and it seems the point is in the binding of variable V_NUM. But I don't know the exact reason. I think maybe it relates with the parse of PL/SQL. Would someone please help me or give me some hints?

Answer 1

hi,
When you saye,
   MERGE INTO TBL_A A
    USING (SELECT V_NUM,
                  COL1,
                  COL2
             FROM TBL_B) B
       ON (A.COL1 = V_NUM)
   WHEN MATCHED
   THEN
      UPDATE SET A.COL2 = B.COL2;
In the above for ON (A.COL1 = V_NUM)
oracle treats v_num as a variable in the procedure rather than v_num returned from using clause.
So you need to alias that.
MERGE INTO TBL_A A
    USING (SELECT V_NUM as somecol,
                  COL1,
                  COL2
             FROM TBL_B) B
       ON (A.COL1 = b.somecol)
   WHEN MATCHED
   THEN
      UPDATE SET A.COL2 = B.COL2;Edited by: Ganesh Srivatsav on May 12, 2011 11:42 AM
Added alias after peter pointed out for variable in the using.