In most databases, there will be dependencies between objects in the database. Sometimes, we need to understand those dependencies to figure out how to perform certain actions. Let's look at this in detail.
We'll use the following simple database to understand the issues and investigate them. There are two tables, as follows:
CREATE TABLE orders (orderid integer PRIMARY KEY); CREATE TABLE orderlines (orderid integer,lineid smallint,PRIMARY KEY (orderid, lineid));
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);
If we try to drop the referenced table, we get the following message: ...