PostgreSQL 11 Administration Cookbook

Getting ready

We'll use the following simple database to understand and investigate them:

1. Create two tables as follows:

CREATE TABLE orders (orderid integer PRIMARY KEY);CREATE TABLE orderlines (orderid integer,lineid smallint,PRIMARY KEY (orderid, lineid));

2. Now, we add a link between them to enforce what is known as referential integrity, as follows:

ALTER TABLE orderlines ADD FOREIGN KEY (orderid)REFERENCES orders (orderid);

3. If we try to drop the referenced table, we get the following message:

DROP TABLE orders;ERROR: cannot drop table orders because other objects depend on itDETAIL: constraint orderlines_orderid_fkey on table orderlines depends on table ordersHINT: Use DROP ... CASCADE to drop the dependent objects too.

Be ...