Why do we need to worry about the data types we're storing in a database? Well mainly because it helps you with database design.

Adding data to a database is quite easy. The easiest way to do it with php is through a form on a website.

Now we can add data to the database we'll look at how to retrieve it.

How do we update information already in our database? Here's a look at it.

Deleting old data from your database is a useful thing to do. If you keep a list of books or cd's you own and you sell or give something away, you can remove it from the list.

Database indexes help speed up retrieval of data, they can significantly improve performance - the other great benefit of that is your server doesn't have to work as hard to get the data.

Setting up multiple tables in a database is an easy way to keep related data together.

As is the case with most modern relational languages, SQL is based on the tuple relational calculus. As a result every query that can be formulated using the tuple relational calculus (or equivalently, relational algebra) can also be formulated using SQL.

In the previous section (Relational Data Model Formalities).