Optimize SQL that uses between clause

Question

Consider the following 2 tables:

Table A:
id
event_time

Table B
id
start_time
end_time

Every record in table A is mapped to exactly 1 reco

Answer 1

If you can't change the schema -- in particular, if you can't add an index on a.event_time, I don't see much room for improvement at the SQL level.

I'd be more inclined to do it in code.

• read all B start/end/id tuples into a list, sorted on start time
• read all A events
• for each A event
• • find the largest start time <= event time (binary search will do fine)
• • if the event time is <= end time, add A to this B's list of events
• • else this B has no home