"The Empty String vs. Null"

One of the people I sit next to was taking part in some training today, for an End-User Report Writer course.  This course trains clients who buy our system how to write their own reports.  As you can imagine, some people excel at the course and others flop miserably as they fail to grasp the underlying themes of databases, computers and reports.

One of the more academic parts of the course is distinguishing between null and an empty string.  A string is a sequence of zero or more characters.  A string of zero characters is known as the empty string, but is still an existing string.  Null means that there is no string.

If the above explanation was a bit confusing, think of it in terms of fruit bowls.  A string contains a collection of characters just like a fruit bowl contains a collection of fruit.  The empty string is like an empty fruit bowl; the bowl is there but there is no fruit in it.  Null is where there is no fruit bowl, so we can’t even start to look in it to tell if anything is there.