问防止插入额外的子行

EN

CREATE TABLE parent1
(id INT PRIMARY KEY)

CREATE TABLE child1
(id INT
,parent_id INT
)
GO

ALTER TABLE child1 ADD CONSTRAINT chilld1fk FOREIGN KEY (parent_id)
REFERENCES parent1 (id)
GO


CREATE TRIGGER trg_child1
ON child1
INSTEAD OF INSERT
AS

        SELECT parent_id
        FROM child1 AS c
        WHERE EXISTS (SELECT 1
                      FROM inserted AS i
                      WHERE i.parent_id = c.parent_id
                     )

        IF @@ROWCOUNT > 0
            BEGIN
                RAISERROR('You cannot amend this request',16,1)
            END
        ELSE        
            BEGIN
                INSERT child1
                SELECT id
                       ,parent_id
                FROM inserted
            END
GO                                                            

BEGIN TRAN
        INSERT parent1
        VALUES (1)

        INSERT child1 
        (id
        ,parent_id
        )
        SELECT 10,1
        UNION SELECT 11,1        
COMMIT

-- attempting to insert another child outside the transaction
-- will result in an error
INSERT child1
SELECT 12,1

SELECT * FROM child1