https://learninghub.kx.com/forums/topic/asof-join-exercise-11-session-2-kdb-q-developer-level-1
for Exercise 11 of Asof Join in Session 2 of kdb+/q Developer (Level 1), shall we use ``aj0` instead of `aj` to keep the real `pickup_time` in the actual record (jan09, the right-hand table) instead of the boundary time