SQL Antipatterns

Legitimate Uses of the Antipattern

Using null is not the antipattern; the antipattern is using null like an ordinary value or using an ordinary value like null.

One situation where you need to treat null as an ordinary value is when you import or export external data. In a text file with comma-separated fields, all values must be represented by text. For example, in MySQL’s mysqlimport tool for loading data from a text file, \N represents a null.

Similarly, user input cannot represent a null directly. An application that accepts user input may provide a way to map some special input sequence to null. For example, Microsoft .NET 2.0 and newer supports a property called ConvertEmptyStringToNull for web user interfaces. Parameters and bound ...