SQL · Meta · Medium
You are given three tables that describe an ad-serving system. ad holds ad metadata (ad_id is its primary key), impression records one showing of an ad to a user (impression_id is its primary key, and ts holds that showing's moment as 'YYYY-MM-DD HH:MM:SS'), and conversion records a conversion traced back to the impression that produced it (conversion_id is its primary key, with the conversion moment in ts and the money it generated in revenue). Ad performance must be…
Checking your access…