What is Database Hierarchy?
Imagine a set of tables that hold information on a product database. Some items beg to be related in a parent-child relationship, for instance, manufacturers and products. Each manufacturer can have several products, or children. Since each product can only belong to one manufacturer; it will have only one parent. This is the idea behind relational databases, something which has been in use for quite some time. In practice, however, things aren’t so easy. We can set all kinds of foreign key relationships to enforce this bond between tables, but those relationships don’t do much for you except to make sure you don’t input random information. We need a way to take this parent-child relationship to the next step, and take it out of theory and put it into practice.
