As report writers, we often do not have the ability to change the data on the database directly; we merely have to work with the data we’ve got. For this reason, we spend much of our time trying to cosmetically “fix” the data just enough so our report can run properly.
This is especially true of Nulls.
Nulls are the absence of data – as if someone skipped that cell in the database. The tricky part is that Nulls are not equal to zero. In fact, Nulls are not equal to any value.
This is a problem because throughout other reporting practices, Nulls wreak havoc! The most common example of this havoc is if you concatenate several strings of text (essentially gluing pieces of text together into one long text), a single Null in any part of the concatenation will make the whole result Null. In this latter case, imagine concatenating first names, middle initials, and last names into one field called “full name”; not everyone has a middle initial, and if the database has Nulls in the middle initial column, then some people will get Nulls for the “full name” field. It’s like saying “just because you don’t have a middle initial, you don’t get a full name.” And that’s just not fair!