# $597. 好友申请 I：总体通过率
# https://leetcode-cn.com/problems/friend-requests-i-overall-acceptance-rate/

# SQL架构
Create table If Not Exists FriendRequest (sender_id int, send_to_id int, request_date date);
Create table If Not Exists RequestAccepted (requester_id int, accepter_id int, accept_date date);
Truncate table FriendRequest;
insert into FriendRequest (sender_id, send_to_id, request_date) values ('1', '2', '2016/06/01');
insert into FriendRequest (sender_id, send_to_id, request_date) values ('1', '3', '2016/06/01');
insert into FriendRequest (sender_id, send_to_id, request_date) values ('1', '4', '2016/06/01');
insert into FriendRequest (sender_id, send_to_id, request_date) values ('2', '3', '2016/06/02');
insert into FriendRequest (sender_id, send_to_id, request_date) values ('3', '4', '2016/06/09');
Truncate table RequestAccepted;
insert into RequestAccepted (requester_id, accepter_id, accept_date) values ('1', '2', '2016/06/03');
insert into RequestAccepted (requester_id, accepter_id, accept_date) values ('1', '3', '2016/06/08');
insert into RequestAccepted (requester_id, accepter_id, accept_date) values ('2', '3', '2016/06/08');
insert into RequestAccepted (requester_id, accepter_id, accept_date) values ('3', '4', '2016/06/09');
insert into RequestAccepted (requester_id, accepter_id, accept_date) values ('3', '4', '2016/06/10');

# Write your MySQL query statement below
select
    round(
        ifnull(
            (
                select
                    count(*)
                from
                    (
                        select
                            distinct requester_id,
                            accepter_id
                        from
                            RequestAccepted
                    ) as a
            ) / (
                select
                    count(*)
                from
                    (
                        select
                            distinct sender_id,
                            send_to_id
                        from
                            FriendRequest
                    ) as b
            ),
            0
        ),
        2
    ) as accept_rate;

# clean-up
drop table FriendRequest;
drop table RequestAccepted;