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

I wouldn't normally recommend a query like this, but...

Since you've specified that table A only has about 980 rows and that each row maps to exactly one row in table B, then you could do the following and it will most likely be a lot faster than a cartesian join:

SELECT A.id AS id_from_a,
    (
        SELECT B.id
        FROM B
        WHERE A.event_time BETWEEN B.start_time AND B.end_time
        LIMIT 0, 1
    ) AS id_from_b
FROM A