I would say the bit type is a logical data type in SQL Server. Only possible values of 0 or 1.

>The datetime fields cannot be empty in SQL Server. Usually NULLs are used instead in which case IS NULL operator cabn be used.
>There're no logical data type in SQL Server. You can use any integer field instead.
>

IF someDateField IS NULL
>...
>IF someLogicalField = 0
>

>