On most SQL servers you have three values for bool, TRUE, FALSE, and NULL. There is either nullable or non-nullable types of bool, but at some stage you'll need

On most SQL servers you have three values for bool, TRUE, FALSE, and NULL. There is either nullable or non-nullable types of bool, but at some stage you'll need the nullable one so it is useful to have the triple implementation in the language (particularly for an entity framework implementation). For example C# now supports this via their (bool?) type (i.e. nullable bool). However the default language construct is just a two value bool (bool).