1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
| CREATE TABLE T1
(A INT PRIMARY KEY,
B INT);
CREATE TABLE T2
(C INT PRIMARY KEY,
D INT FOREIGN KEY REFERENCES T1 (A)
ON UPDATE CASCADE
ON DELETE CASCADE);
INSERT INTO T1 VALUES (1, 1);
INSERT INTO T1 VALUES (2, 2);
INSERT INTO T2 VALUES (3, NULL);
INSERT INTO T2 VALUES (4, 1);
DELETE FROM T1
WHERE A = 1;
SELECT *
FROM T2;
C D
----------- -----------
3 NULL
CREATE TABLE T3 (E INT PRIMARY KEY,
F INT FOREIGN KEY REFERENCES T2 (C)
ON UPDATE CASCADE
ON DELETE CASCADE)
INSERT INTO T1 VALUES (1, 1);
INSERT INTO T2 VALUES (4, 1);
INSERT INTO T3 VALUES (5, 4);
DELETE FROM T1
WHERE A = 1;
SELECT *
FROM T2;
SELECT *
FROM T3;
CREATE TABLE T4 (G INT PRIMARY KEY,
H INT FOREIGN KEY REFERENCES T2 (C)
ON UPDATE CASCADE
ON DELETE CASCADE);
INSERT INTO T1 VALUES (1, 1);
INSERT INTO T2 VALUES (4, 1);
INSERT INTO T3 VALUES (5, 4);
INSERT INTO T4 VALUES (6, 4);
DELETE FROM T1
WHERE A = 1;
SELECT *
FROM T2;
SELECT *
FROM T3;
SELECT *
FROM T4; |
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