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

MySQL doesn't let you to use INDEX ORDER BY WITH RANGE in derived queries.

That's why you'll need to create a user defined function.

Note that if your ranges do overlap, the query will only select one (which started last).

CREATE UNIQUE INDEX ux_b_start ON b (start_date);

CREATE FUNCTION `fn_get_last_b`(event_date TIMESTAMP) RETURNS int(11)
BEGIN
  DECLARE id INT;
  SELECT b.id
  INTO id
  FROM b
  FORCE INDEX (ux_b_start)
  WHERE b.start_time <= event_date
  ORDER BY
    b.start_time DESC
  LIMIT 1;
  RETURN id;
END;

SELECT COUNT(*) FROM a;

1000


SELECT COUNT(*) FROM b;

200000

SELECT *
FROM (
  SELECT fn_get_last_b(a.event_time) AS bid,
         a.*
  FROM a
) ao, b FORCE INDEX (PRIMARY)
WHERE b.id = ao.bid
  AND b.end_time >= ao.event_time

1000 rows fetched in 0,0143s (0,1279s)