Second SELECT query if first SELECT returns 0 rows

Question

I am trying to speed up a PHP script and I am currently pushing some PHP logic in the Mysql domain of the thing. Is there a way to make a different select query if the first

Answer 1

In a general case where you have multiple values for A (lets say, 'B', 'C', 'D', 'E', etc.) and you want to retrieve only the rows that belong to the lowest value that exists, then you would use the following query. This will work also for the particular case you exposed.

SELECT p1.*
FROM proxies p1
LEFT JOIN proxies p2
    ON p1.A > p2.A
WHERE p2.A IS NULL

Fiddle