'Disabled' constraints preventing MERGE OUTPUT from working - sql

Question

CREATE TABLE a(
id INT PRIMARY KEY IDENTITY(1,1),
val INT
);
CREATE TABLE b(
id INT PRIMARY KEY IDENTITY(1,1),
val INT
);
CREATE TABLE a_b(
fk_a INT,
fk_b INT
);
CREATE TABLE c(
id INT PRIMARY KEY IDENTITY(1,1),
a_val INT,
b_val INT
);
ALTER TABLE a_b ADD CONSTRAINT fk_a_b_fk_a FOREIGN KEY (fk_a) REFERENCES a(id);
ALTER TABLE a_b ADD CONSTRAINT fk_a_b_fk_b FOREIGN KEY (fk_b) REFERENCES b(id);
INSERT INTO a(val) VALUES (1), (2), (3);
INSERT INTO b(val) VALUES (2), (4), (6);
ALTER TABLE a_b NOCHECK CONSTRAINT ALL;
WITH cte AS (
SELECT
a.id AS 'a_id',
a.val AS 'a_val',
b.id AS 'b_id',
b.val AS 'b_val'
FROM a
INNER JOIN b
ON a.id = b.id
)
MERGE INTO c
USING cte ON 1 = 0
WHEN NOT MATCHED THEN
INSERT (a_val, b_val)
VALUES (cte.a_val, cte.b_val)
OUTPUT cte.a_id, cte.b_id INTO a_b(fk_a, fk_b);
ALTER TABLE a_b WITH CHECK CHECK CONSTRAINT ALL;
SELECT * FROM c;
The error I'm getting is:
The target table 'a_b' of the OUTPUT INTO clause cannot be on either side of a (primary key, foreign key) relationship. Found reference constraint 'fk_a_b_fk_a'.
However, I'm very clearly disabling the constraints surrounding the merge statement. Is there any way to fix this?
The same thing goes for/is happening with triggers and disabling them surrounding the merge statement doesn't work.

Answer 1

try this
CREATE TABLE #a(
id INT PRIMARY KEY IDENTITY(1,1),
val INT
);
CREATE TABLE #b(
id INT PRIMARY KEY IDENTITY(1,1),
val INT
);
CREATE TABLE #a_b(
fk_a INT,
fk_b INT
);
CREATE TABLE #c(
id INT PRIMARY KEY IDENTITY(1,1),
a_val INT,
b_val INT
);
ALTER TABLE #a_b ADD CONSTRAINT fk_a_b_fk_a FOREIGN KEY (fk_a) REFERENCES a(id);
ALTER TABLE #a_b ADD CONSTRAINT fk_a_b_fk_b FOREIGN KEY (fk_b) REFERENCES b(id);
INSERT INTO #a(val) VALUES (1), (2), (3);
INSERT INTO #b(val) VALUES (2), (4), (6);
WITH cte AS (
SELECT
a.id AS 'a_id',
a.val AS 'a_val',
b.id AS 'b_id',
b.val AS 'b_val'
FROM #a a
INNER JOIN #b b
ON a.id = b.id
)
MERGE INTO #c
USING cte ON 1 = 0
WHEN NOT MATCHED THEN
INSERT (a_val, b_val)
VALUES (cte.a_val, cte.b_val)
OUTPUT cte.a_id, cte.b_id INTO #a_b(fk_a, fk_b);
SELECT * FROM #c;