编辑代码

CREATE DATABASE test;
use test;
CREATE TABLE RequestAccepted (
	requester_id int,
    accepter_id int,
	accept_date date
);

INSERT INTO RequestAccepted VALUES (1,2,'2016/06/03');
INSERT INTO RequestAccepted VALUES (1,3,'2016/06/08');
INSERT INTO RequestAccepted VALUES (2,3,'2016/06/08');
INSERT INTO RequestAccepted VALUES (3,4,'2016/06/09');
select id,count(*) as count_num from
(
select requester_id as id from RequestAccepted 
union all
select accepter_id as id from RequestAccepted
)t1
group by t1.id order by count_num desc limit 1
;