I am using `SQL Server 2014`. Below is an extract of Table `t1`:

```
rownum    RoomID    ArrivalDate    DepartureDate     Name     GuestID
  1         287     2020-01-01      2020-01-09       John      600
  2         451     2020-01-09      2020-01-10       John      600
  3         458     2020-01-09      2020-01-10       John      600
  1         240     2020-03-19      2020-03-21       Alan      112
  2         159     2020-03-21      2020-03-22       Alan      112
  1         400     2020-05-01      2020-05-10       Joe       225
  2         155     2020-06-13      2020-06-18       Joe       225
  1         200     2020-07-01      2020-07-08       Smith     980
  2         544     2020-07-08      2020-07-10       Smith     980
  3         428     2020-09-01      2020-09-05       Smith     980
  ...

```

The problem: I need to filter this table so that the output gives me only those rows of a guest where the difference/s between his ArrivalDate (at rownum 2 or 3 or 4...) and his DepartureDate (at rownum =1) is greater than 0.

To simplify: If we take Guest John, his ArrivalDate for rownum=2 and rownum=3 are both the same as his DepartureDate for rownum=1; therefore I want to exclude him completely in my output. Same for Guest Allan. However, for Guest Smith only where the rownum=2 needs to be excluded.

Note: all guests in this table will have at least a rownum=2 (that is, a minimum of 2 entries).

My expected output:

```
 rownum     RoomID    ArrivalDate     DepartureDate   Name    GuestID
   1         400       2020-05-01      2020-05-10     Joe       225
   2         155       2020-06-13      2020-06-18     Joe       225
   1         200       2020-07-01      2020-07-08     Smith     980         
   3         428       2020-09-01      2020-09-05     Smith     980

```

I am stuck on how to write the logic behind this filter. Any help would be appreciated.