I have a table like this:

```
OrderID | PhaseID | Timestamp
1       | 1       | 1/1
1       | 2       | 1/2
1       | 3       | 1/3
1       | 2       | 1/4
1       | 4       | 1/5

```

I'm trying to get a query to return the most recent timestamp for each orderphase combination without being followed by a lesser phaseid. Something like this:

```
OrderID | PhaseID | MaxTimestampWithoutBeingFollowedByLesserPhaseID
1       | 1       | 1/1
1       | 2       | 1/4
1       | 3       | NULL
1       | 4       | 1/5

```

I keep running around in circles and coming up with this problem of a conditional aggregate query.

Can anybody figure out the query or give me some pointers?