forked from huawei/openGauss-server
83 lines
2.1 KiB
Plaintext
83 lines
2.1 KiB
Plaintext
--Column ID of table A is primary key:
|
|
|
|
CREATE TABLE A (
|
|
ID int4 not null
|
|
);
|
|
CREATE UNIQUE INDEX AI ON A (ID);
|
|
|
|
--Columns REFB of table B and REFC of C are foreign keys referenting ID of A:
|
|
|
|
CREATE TABLE B (
|
|
REFB int4
|
|
);
|
|
CREATE INDEX BI ON B (REFB);
|
|
|
|
CREATE TABLE C (
|
|
REFC int4
|
|
);
|
|
CREATE INDEX CI ON C (REFC);
|
|
|
|
--Trigger for table A:
|
|
|
|
CREATE TRIGGER AT BEFORE DELETE OR UPDATE ON A FOR EACH ROW
|
|
EXECUTE PROCEDURE
|
|
check_foreign_key (2, 'cascade', 'ID', 'B', 'REFB', 'C', 'REFC');
|
|
/*
|
|
2 - means that check must be performed for foreign keys of 2 tables.
|
|
cascade - defines that corresponding keys must be deleted.
|
|
ID - name of primary key column in triggered table (A). You may
|
|
use as many columns as you need.
|
|
B - name of (first) table with foreign keys.
|
|
REFB - name of foreign key column in this table. You may use as many
|
|
columns as you need, but number of key columns in referenced
|
|
table (A) must be the same.
|
|
C - name of second table with foreign keys.
|
|
REFC - name of foreign key column in this table.
|
|
*/
|
|
|
|
--Trigger for table B:
|
|
|
|
CREATE TRIGGER BT BEFORE INSERT OR UPDATE ON B FOR EACH ROW
|
|
EXECUTE PROCEDURE
|
|
check_primary_key ('REFB', 'A', 'ID');
|
|
|
|
/*
|
|
REFB - name of foreign key column in triggered (B) table. You may use as
|
|
many columns as you need, but number of key columns in referenced
|
|
table must be the same.
|
|
A - referenced table name.
|
|
ID - name of primary key column in referenced table.
|
|
*/
|
|
|
|
--Trigger for table C:
|
|
|
|
CREATE TRIGGER CT BEFORE INSERT OR UPDATE ON C FOR EACH ROW
|
|
EXECUTE PROCEDURE
|
|
check_primary_key ('REFC', 'A', 'ID');
|
|
|
|
-- Now try
|
|
|
|
INSERT INTO A VALUES (10);
|
|
INSERT INTO A VALUES (20);
|
|
INSERT INTO A VALUES (30);
|
|
INSERT INTO A VALUES (40);
|
|
INSERT INTO A VALUES (50);
|
|
|
|
INSERT INTO B VALUES (1); -- invalid reference
|
|
INSERT INTO B VALUES (10);
|
|
INSERT INTO B VALUES (30);
|
|
INSERT INTO B VALUES (30);
|
|
|
|
INSERT INTO C VALUES (11); -- invalid reference
|
|
INSERT INTO C VALUES (20);
|
|
INSERT INTO C VALUES (20);
|
|
INSERT INTO C VALUES (30);
|
|
|
|
DELETE FROM A WHERE ID = 10;
|
|
DELETE FROM A WHERE ID = 20;
|
|
DELETE FROM A WHERE ID = 30;
|
|
|
|
SELECT * FROM A;
|
|
SELECT * FROM B;
|
|
SELECT * FROM C;
|