SQL Query to Join Two Tables Based Off Closest Timestamp

Question

I have two tables in SQL and I need to be able to do a join based off of the timestamp in table B that is earlier than or equal to the timestamp in table A.

So, here

Answer 1

SELECT case.id, case.resolution, case.timestamp, class.value
  FROM closed_cases AS case
  LEFT JOIN classifications AS class 
  ON case.timestamp >= class.timestamp
  WHERE case.timestamp BETWEEN $1 AND $2;