Databases store data, this we already know. However we have not looked at how we communicate with the database. There is also the question of how the data is stored however this question is outside the scope of this course.

Some of you may of only ever seen graphical front ends to databases. However these are not how we communicate with the data base. We use a special language to communicate with the database. What the front ends do is use the language to communicate with the database. The diagram shows this below.

The end result is always the same. On the diagram the big arrow is labelled with the acronyms DML and DDL. These stand for data manipulation language and data definition language. We shall look at how these work using SQL (Structured query language).