LC 0597 [E] Friend Requests I: Overall Acceptance Rate - ALawliet/algorithms GitHub Wiki
SELECT
ROUND(
IFNULL(
(SELECT DISTINCT COUNT(*) FROM (SELECT DISTINCT requester_id, accepter_id FROM RequestAccepted) AS A)
/
(SELECT DISTINCT COUNT(*) FROM (SELECT DISTINCT sender_id, send_to_id FROM FriendRequest) AS B),
0)
, 2) AS accept_rate;