codekingpro/portable-devtools

1--Column ID of table A is primary key:2 3CREATE TABLE A (4	ID	int4 not null5);6CREATE UNIQUE INDEX AI ON A (ID);7 8--Columns REFB of table B and REFC of C are foreign keys referencing ID of A:9 10CREATE TABLE B (11	REFB	int412);13CREATE INDEX BI ON B (REFB);14 15CREATE TABLE C (16	REFC	int417);18CREATE INDEX CI ON C (REFC);19 20--Trigger for table A:21 22CREATE TRIGGER AT BEFORE DELETE OR UPDATE ON A FOR EACH ROW23EXECUTE PROCEDURE24check_foreign_key (2, 'cascade', 'ID', 'B', 'REFB', 'C', 'REFC');25/*262	- means that check must be performed for foreign keys of 2 tables.27cascade	- defines that corresponding keys must be deleted.28ID	- name of primary key column in triggered table (A). You may29	  use as many columns as you need.30B	- name of (first) table with foreign keys.31REFB	- name of foreign key column in this table. You may use as many32	  columns as you need, but number of key columns in referenced33	  table (A) must be the same.34C	- name of second table with foreign keys.35REFC	- name of foreign key column in this table.36*/37 38--Trigger for table B:39 40CREATE TRIGGER BT BEFORE INSERT OR UPDATE ON B FOR EACH ROW41EXECUTE PROCEDURE42check_primary_key ('REFB', 'A', 'ID');43 44/*45REFB	- name of foreign key column in triggered (B) table. You may use as46	  many columns as you need, but number of key columns in referenced47	  table must be the same.48A	- referenced table name.49ID	- name of primary key column in referenced table.50*/51 52--Trigger for table C:53 54CREATE TRIGGER CT BEFORE INSERT OR UPDATE ON C FOR EACH ROW55EXECUTE PROCEDURE56check_primary_key ('REFC', 'A', 'ID');57 58-- Now try59 60INSERT INTO A VALUES (10);61INSERT INTO A VALUES (20);62INSERT INTO A VALUES (30);63INSERT INTO A VALUES (40);64INSERT INTO A VALUES (50);65 66INSERT INTO B VALUES (1);	-- invalid reference67INSERT INTO B VALUES (10);68INSERT INTO B VALUES (30);69INSERT INTO B VALUES (30);70 71INSERT INTO C VALUES (11);	-- invalid reference72INSERT INTO C VALUES (20);73INSERT INTO C VALUES (20);74INSERT INTO C VALUES (30);75 76DELETE FROM A WHERE ID = 10;77DELETE FROM A WHERE ID = 20;78DELETE FROM A WHERE ID = 30;79 80SELECT * FROM A;81SELECT * FROM B;82SELECT * FROM C;83