ORA-00903 when merging on an updatable view - sql

Question

I get an ORA-00903 when merging into an otherwise updatable view in Oracle 11gR2 (USER_UPDATABLE_COLUMNS shows all columns insertable, updatable, deletable for base and view)
Standard Insert, Update, Delete all work normally.
The docs:
http://docs.oracle.com/cd/E11882_01/server.112/e41084/statements_9016.htm#SQLRF01606
has the following:
Use the INTO clause to specify the target table or view you are
updating or inserting into. In order to merge data into a view, the
view must be updatable. Refer to "Notes on Updatable Views" for more
information.
The updatable view criteria appear to be met in the following example, but the ORA-00903 is present in all merge attempts. Changes to the instead of trigger don't appear to have any impact on mergability.
CREATE TABLE MERGE_TEST_B
(MERGE_TEST_ID NUMBER NOT NULL PRIMARY KEY,
MERGE_TEST_DESC VARCHAR2(50) UNIQUE NOT NULL);
CREATE OR REPLACE VIEW MERGE_TEST_V
AS
SELECT
MERGE_TEST_B.MERGE_TEST_ID,
MERGE_TEST_B.MERGE_TEST_DESC
FROM MERGE_TEST_B;
CREATE OR REPLACE TRIGGER MERGE_TEST_V_TIX
INSTEAD OF INSERT OR UPDATE OR DELETE ON MERGE_TEST_V
FOR EACH ROW
BEGIN
DBMS_OUTPUT.PUT_LINE('TESTING VIEW MERGE.');
END;
/
I wondered if there is a change that can can get this view into a mergable state, or whether this is ineligible.
The following attempt fails:
MERGE INTO MERGE_TEST_V
USING
(SELECT
'TESTMERGE' MERGE_TEST_DESC
FROM DUAL) TEST_DATA
ON (MERGE_TEST_V.MERGE_TEST_DESC = TEST_DATA.MERGE_TEST_DESC)
WHEN NOT MATCHED THEN INSERT
(MERGE_TEST_ID, MERGE_TEST_DESC)
VALUES
(-100, TEST_DATA.MERGE_TEST_DESC);
Any ideas would be appreciated.
Thanks

Answer 1

I'm not sure why Oracle returns ORA-00903 instead of ORA-38106, but the issue appears to be your trigger. Dropping the trigger will allow your merge to work.
According to the description of ORA-38106, "When using MERGE to modify a view, you must only specify a single table in the view, and the view cannot have an INSTEAD OF trigger." [emphasis mine]
Almost buried in the documentation on the merge statement, this is actually mentioned