这里是我的简化。假设时间间隔

       | |
     | |

不要重叠，xa<xb和ya<yb可以简化处理。上述条件可以简单检查。然后你会得到

      ya       yb
      |--------|
xa |--|xb
   |----|
         |----|
ya > xa => return ya - xa < xb - xa
else    => return xa < yb

正如您可能注意到的，第二个间隔仅在xa>=ya的情况下相关。

只要有简单的解决方案，仅仅使用额外的包来做简单的事情可能效率不高。但是，如果您已经在项目中使用了日期fns，那么有一个名为areIntervalsOverlapping的方法也会执行同样的操作。

语法：

areIntervalsOverlapping(intervalLeft, intervalRight, [options])

例子：

// For overlapping time intervals:
areIntervalsOverlapping(
  { start: new Date(2014, 0, 10), end: new Date(2014, 0, 20) },
  { start: new Date(2014, 0, 17), end: new Date(2014, 0, 21) }
)
//=> true

简单的解决方案：

compare the two dates: 
    A = the one with smaller start date, B = the one with bigger start date
if(A.end < B.start)
    return false
return true

如果您使用的日期范围尚未结束（仍在进行中），例如未设置endDate='0000-00-00'您不能使用BETWEEN，因为0000-00-00不是有效日期！

我使用了这个解决方案：

(Startdate BETWEEN '".$startdate2."' AND '".$enddate2."')  //overlap: starts between start2/end2
OR (Startdate < '".$startdate2."' 
  AND (enddate = '0000-00-00' OR enddate >= '".$startdate2."')
) //overlap: starts before start2 and enddate not set 0000-00-00 (still on going) or if enddate is set but higher then startdate2

如果startdate2高于enddate，则没有重叠！

这里有一个可以在本地使用的通用方法。

    // Takes a list and returns all records that have overlapping time ranges.
    public static IEnumerable<T> GetOverlappedTimes<T>(IEnumerable<T> list, Func<T, bool> filter, Func<T,DateTime> start, Func<T, DateTime> end)
    {
        // Selects all records that match filter() on left side and returns all records on right side that overlap.
        var overlap = from t1 in list
                      where filter(t1)
                      from t2 in list
                      where !object.Equals(t1, t2) // Don't match the same record on right side.
                      let in1 = start(t1)
                      let out1 = end(t1)
                      let in2 = start(t2)
                      let out2 = end(t2)
                      where in1 <= out2 && out1 >= in2
                      let totover = GetMins(in1, out1, in2, out2)
                      select t2;

        return overlap;
    }

    public static void TestOverlap()
    {
        var tl1 = new TempTimeEntry() { ID = 1, Name = "Bill", In = "1/1/08 1:00pm".ToDate(), Out = "1/1/08 4:00pm".ToDate() };
        var tl2 = new TempTimeEntry() { ID = 2, Name = "John", In = "1/1/08 5:00pm".ToDate(), Out = "1/1/08 6:00pm".ToDate() };
        var tl3 = new TempTimeEntry() { ID = 3, Name = "Lisa", In = "1/1/08 7:00pm".ToDate(), Out = "1/1/08 9:00pm".ToDate() };
        var tl4 = new TempTimeEntry() { ID = 4, Name = "Joe", In = "1/1/08 3:00pm".ToDate(), Out = "1/1/08 8:00pm".ToDate() };
        var tl5 = new TempTimeEntry() { ID = 1, Name = "Bill", In = "1/1/08 8:01pm".ToDate(), Out = "1/1/08 8:00pm".ToDate() };
        var list = new List<TempTimeEntry>() { tl1, tl2, tl3, tl4, tl5 };
        var overlap = GetOverlappedTimes(list, (TempTimeEntry t1)=>t1.ID==1, (TempTimeEntry tIn) => tIn.In, (TempTimeEntry tOut) => tOut.Out);

        Console.WriteLine("\nRecords overlap:");
        foreach (var tl in overlap)
            Console.WriteLine("Name:{0} T1In:{1} T1Out:{2}", tl.Name, tl.In, tl.Out);
        Console.WriteLine("Done");

        /*  Output:
            Records overlap:
            Name:Joe T1In:1/1/2008 3:00:00 PM T1Out:1/1/2008 8:00:00 PM
            Name:Lisa T1In:1/1/2008 7:00:00 PM T1Out:1/1/2008 9:00:00 PM
            Done
         */
    }

答案对我来说太简单了，所以我创建了一个更通用的动态SQL语句，用于检查某人是否有重叠的日期。

SELECT DISTINCT T1.EmpID
FROM Table1 T1
INNER JOIN Table2 T2 ON T1.EmpID = T2.EmpID 
    AND T1.JobID <> T2.JobID
    AND (
        (T1.DateFrom >= T2.DateFrom AND T1.dateFrom <= T2.DateTo) 
        OR (T1.DateTo >= T2.DateFrom AND T1.DateTo <= T2.DateTo)
        OR (T1.DateFrom < T2.DateFrom AND T1.DateTo IS NULL)
    )
    AND NOT (T1.DateFrom = T2.DateFrom)