Say I have this schema

CREATE TABLE temp (
EntityId BIGINT AUTO_INCREMENT PRIMARY KEY,
CreationTime DEFAULT NOW()
);

Now let's say I want to find all rows created within the last 24 hours. If I do

select * from temp where CreationTime > DATE_SUB(NOW(), INTERVAL 24 HOUR)

that's going to do a full table scan to find out, even though there's
already an implicit ordering in EntityId (this is of course assuming I
don't manually set CreationTime to something else). Is there any way
to take advantage of the fact that there's a primary key index on
entityId, or do I have to put a secondary index on CreationTime?

Thanks,
Waynn