关系的主键

根据您的评论,您可能应该在插入之前进行检查。没有一个真正好的约束可以用来防止重复插入。

declare @Keeper_Number int = 5
declare @Enclosure_Number int = 2
declare @startShift datetime = '20181116 08:00:00'
declare @endShift datetime = '20181116 08:00:00'

if exists(select 1 from ShiftTable 
          where Keeper_Number = @Keeper_Number 
          and (     shiftStart between @startShift and @endShift
                or  shiftEnd between @startShift and @endShift)
        )
begin
    raiserror('Employee is already scheduled in another enclousre during this time',16,1)
    return
end
else
begin
    insert into ShiftTable(Keeper_Number, Enclousre_Number, shiftStart, shiftEnd)
    values(@Keeper_Number, @Enclosure_Number, @startShift, @endShift)
end