null

As we already stated in earlier articles in this blog [1 and 2] it is a good idea to use NULL values properly in MariaDB and MySQL.

In the recent MariaDB DBA advanced training class the question came up if MariaDB can make use of an index when searching for NULL values... And to be honest I was not sure any more. So instead of reading boring documentation I did some little tests:

Search for NULL

First I started with a little test data set. Some of you might already know it:

Abstract:

It is common practice in MySQL table design that fields are declared as NOT NULL but some non-sense DEFAULT values are specified for unknown field contents. In this article we show why this behavior is non optimal an why you should better declare a field to allow NULL values and use NULL values instead of some dummy values.