Hibernate Basic value types 'yes_no' and 'true_false'

In Hibernate a lot of Basic value types. One of them is 'yes_no' and 'true_false'. And I was wondering what the fundamental difference between these two types? I see that in the database for the type of 'yes_no' written 'Y or N' and from 'true_false' written 'F or T' and no more difference. Then why do we need these tw开发者_如何学Co types? Why can not we do just one?

It's a convenience for mapping legacy database schemas.

If you have a legacy database schema where boolean values are represented as T/F, you use true_false. If they are represented as Y/N, you use yes_no.