After some testing I realized that the support of database constraints
is partial
and therefore potentially dangerous!
If I continue my example with statement
DELETE FROM B WHERE AID = 1;
the statement goes through
but now the table C is in violation of constraint DB_CONSTRAINT CHECK.
and executing a statement like
UPDATE C SET AID = 1 WHERE AID = 1
throws a constraint violation.
- rami
31.8.2011 19:20, Rami Ojares kirjoitti:
Hi,
I always thought that H2 does not support database wide constraints
except through triggers.
(namely constraints that can depend on the state of the whole database).
But I just realized that it does.
So I thought that this could be brought out more in the documentation
because I think it is A BIG FEATURE!
Here I have a simple example to verify db constraints.
CREATE TABLE A (ID INT PRIMARY KEY);
CREATE TABLE B (AID INT REFERENCES A);
CREATE TABLE C (
AID INT REFERENCES A,
CONSTRAINT DB_CONSTRAINT CHECK(
EXISTS(
SELECT *
FROM A
JOIN B
ON C.AID = A.ID AND A.ID = B.AID
)
)
);
INSERT INTO A VALUES(1);
INSERT INTO C VALUES(1);
INSERT INTO B VALUES(1);
INSERT INTO C VALUES(1);
The second insert will throw a constraint violation like it should.
Sweet.
- rami
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