Blog 06 – Week 9

This week we are continuing from week 8 and covering subqueries, referential integrity and cascades.

Subqueries are a select statement within another select statement and are used to obtain data from the database that is necessary for the containing query.
Referential integrity allows you to put constraints on the database. For example, it can stop you from deleting data from a table that is required by another set of data in the database.
Cascades are used in the deleting of data and are an extension to referential integrity. This causes the dependant data to be deleted along with the data it is dependant on.