In short (tl;dr): When trying to delete rows during a MERGE, Oracle 10g seems to ignore ON DELETE CASCADE statements for foreign keys. I would like to know if this is a known bug, a feature (apparently discontinued in 11g), or what.
More in detail:
It seems to me that in Oracle XE 10g, trying to delete rows from a table within a MERGE statement leads to an ORA-02292 error (violation of referential integrity) whenever there is a foreign key referencing the destination table of the merge, even if ON DELETE CASCADE was specified in the foreign key constraint.
For example, say I create three tables
CREATE TABLE Mysource(
MykeyS NUMBER,
MystringS VARCHAR2(10),
CONSTRAINT Mysource_PK PRIMARY KEY(MykeyS) ENABLE
);
CREATE TABLE Mydest(
MykeyD NUMBER,
MystringD VARCHAR2(10),
CONSTRAINT Mydest_PK PRIMARY KEY(MykeyD) ENABLE
);
CREATE TABLE Myother(
Mykey NUMBER,
Mydate DATE,
CONSTRAINT Myother_FK FOREIGN KEY(Mykey)
REFERENCES Mydest(MykeyD) ON DELETE CASCADE ENABLE
);
and insert some data in them, then try
MERGE INTO Mydest D
USING Mysource S
ON (D.MykeyD=S.MykeyS)
WHEN MATCHED THEN
UPDATE SET D.MystringD = S.MystringS
DELETE WHERE (S.MykeyS > 10)
WHEN NOT MATCHED THEN
INSERT (MykeyD, MystringD)
VALUES (S.MykeyS, S.MystringS)
WHERE (S.MykeyS <= 10)
If both Mydest and Myother had some rows with >10 key, the attempted MERGE would then result in an ORA-02292, claiming a violation of the Myother_FK constraint.
This sounds illogical to me (I can delete rows from Mydest using a direct DELETE, but not with a MERGE?), and in fact it does not seem to happen with Oracle XE 11g.
Question:
Do you know if this is a known bug, or a weird feature? Or am I missing something, maybe? Searching the internet has not helped much, so far.
Oracle has it listed as bug 8268746 in 10.2.0.3. It is fixed in 11.2. The document is not available for linking externally, but it provides a test case similar to the example provided in the question above. The work-around is to not use the merge statement (or upgrade to 11.2).