использовать вычисленные даты с использованием конверсии:
cast(cast(mydatecolumn as varchar(20)) + ' ' +
cast(mytimecolumn as varchar(20)) as datetime)
выходы, например start_datetime и end_datetime
предполагаемые переменные: @inserted_start_datetime, @inserted_end_datetime, @ name
Insert Into MyTable(<values>)
Where not exists (
select * from table t2
where name = @name
and (@inserted_start_datetime between start_datetime and end_datetime
or @inserted_end_datetime between start_datetime and end_datetime
or start_datetime between @inserted_start_datetime and @inserted_end_datetime
or end_datetime between @inserted_start_datetime and @inserted_end_datetime ))
EDITED