When you are working with database engines with capabilities beyond just retrieving your data, it makes sense to take advantage of these features. Many of these additonal features are derived from many of the elements that have already been covered, such as clauses in the SELECT statement, joins, views, and so on.
Another extremely useful capability is provided by an engine's ability to support functions. Functions are predefined actions that can be used on the values that you send the engine.
For example, at a very simple level, you can query the database with the following, having the database complete some addition for you:

SELECT 5 + 5 

The result would be an unnamed column with a value of 10. The engine actually figures out the results for you, returning them as the answer to your "query."
In this module, you will learn how to use several different kinds of functions, providing help for character-based, numeric, and date-formatted values.