Problem with MERGE statement

Question

Hi All,
We are encountering a strange problem with the merge command.
The following statement works :-
merge into ATTRIBUTE_GROUP@US_PRODUCT_UAT a
using
     select
          a1.group_id,
          a1.NAME,
          a1.CREATE_DATE,
          a1.MODIFY_DATE
     from
          ATTRIBUTE_GROUP_LOG a1,
          product_push_wrk a2
     where
          a2.column_id = a1.group_id and
          a2.modify_date = a1.modify_date ) b
on ( a.group_id = b.group_id)
when matched then
     update set
          a.NAME = b.NAME,
          a.CREATE_DATE = b.CREATE_DATE,
          a.MODIFY_DATE = b.MODIFY_DATE
when not matched then
     insert
          a.group_id,
          a.NAME,
          a.CREATE_DATE,
          a.MODIFY_DATE
     values
          b.group_id,
          b.NAME,
          b.CREATE_DATE,
          b.MODIFY_DATE
However when we change the order of the columns in the select query as follows the an error occurs : -
merge into ATTRIBUTE_GROUP@US_PRODUCT_UAT a
using
     select
          a1.NAME,
          a1.group_id,
          a1.CREATE_DATE,
          a1.MODIFY_DATE
     from
          ATTRIBUTE_GROUP_LOG a1,
          product_push_wrk a2
     where
          a2.column_id = a1.group_id and
          a2.modify_date = a1.modify_date ) b
on ( a.group_id = b.group_id)
when matched then
     update set
          a.NAME = b.NAME,
          a.CREATE_DATE = b.CREATE_DATE,
          a.MODIFY_DATE = b.MODIFY_DATE
when not matched then
     insert
          a.group_id,
          a.NAME,
          a.CREATE_DATE,
          a.MODIFY_DATE
     values
          b.group_id,
          b.NAME,
          b.CREATE_DATE,
          b.MODIFY_DATE
ERROR at line 15:
ORA-00904: "B"."GROUP_ID": invalid identifier
SQL> l 15
15* on ( a.group_id = b.group_id)
The structure of the attribute_log table is as follows :-
SQL> desc ATTRIBUTE_GROUP
Name Null? Type
GROUP_ID NOT NULL NUMBER
NAME NOT NULL VARCHAR2(96)
CREATE_DATE NOT NULL DATE
MODIFY_DATE NOT NULL DATE
Any pointers to the cause of this error will be highly appreciated.
Thanks and Regards,
Suman

Answer 1

The table structures are as follows :-
04:17:17 SQL> desc product_push_wrk
Name Null? Type
COLUMN_ID NOT NULL NUMBER
TYPE NOT NULL VARCHAR2(10)
PARENT_COLUMN_ID NUMBER
LEVEL_NO NUMBER
MODIFY_DATE NOT NULL DATE
04:17:25 SQL> desc ATTRIBUTE_GROUP_LOG
Name Null? Type
GROUP_ID NOT NULL NUMBER
NAME NOT NULL VARCHAR2(96)
CREATE_DATE DATE
MODIFY_DATE DATE
04:18:02 SQL> desc ATTRIBUTE_GROUP
Name Null? Type
GROUP_ID NOT NULL NUMBER
NAME NOT NULL VARCHAR2(96)
CREATE_DATE DATE
MODIFY_DATE DATE