トリガーを使用してチームと人物のテーブルにカウンターを維持する次の方法を検討すると、2人以上のアスリートと2人以上のチームに所属するチームを簡単に見つけることができます。
（注：私はより良いデータの整合性を強制されます複合キーの賛成であなたのアスリートテーブルから代理IDキーを削除した私はteam_athleteするアスリートをも名前を変更しました。）
drop table if exists person;
create table person
(
person_id int unsigned not null auto_increment primary key,
name varchar(255) not null,
team_count smallint unsigned not null default 0
)
engine=innodb;
drop table if exists team;
create table team
(
team_id int unsigned not null auto_increment primary key,
name varchar(255) not null,
athlete_count smallint unsigned not null default 0,
key (athlete_count)
)
engine=innodb;
drop table if exists team_athlete;
create table team_athlete
(
team_id int unsigned not null,
person_id int unsigned not null,
primary key (team_id, person_id), -- note clustered composite PK
key person(person_id) -- added index
)
engine=innodb;
delimiter #
create trigger team_athlete_after_ins_trig after insert on team_athlete
for each row
begin
update team set athlete_count = athlete_count+1 where team_id = new.team_id;
update person set team_count = team_count+1 where person_id = new.person_id;
end#
delimiter ;
insert into person (name) values ('p1'),('p2'),('p3'),('p4'),('p5');
insert into team (name) values ('t1'),('t2'),('t3'),('t4');
insert into team_athlete (team_id, person_id) values
(1,1),(1,2),(1,3),
(2,3),(2,4),
(3,1),(3,5);
select * from team_athlete;
select * from person;
select * from team;
select * from team where athlete_count >= 2;
select * from person where team_count >= 2;
EDIT唯一の2名のチームを含むビューを作成します
：
は次のように最初は誤解質問を追加しました。
drop view if exists teams_with_2_players_view;
create view teams_with_2_players_view as
select
t.team_id,
ta.person_id,
p.name as person_name
from
team t
inner join team_athlete ta on t.team_id = ta.team_id
inner join person p on ta.person_id = p.person_id
where
t.athlete_count = 2;
このビューを使用して、最も頻繁に発生する人のペアを見つけます。
select
p1.person_id as p1_person_id,
p1.person_name as p1_person_name,
p2.person_id as p2_person_id,
p2.person_name as p2_person_name,
count(*) as counter
from
teams_with_2_players_view p1
inner join teams_with_2_players_view p2 on
p2.team_id = p1.team_id and p2.person_id > p1.person_id
group by
p1.person_id, p2.person_id
order by
counter desc;
希望はこのことができます:)
EDIT 2チェックパフォーマンス
select count(*) as counter from person;
+---------+
| counter |
+---------+
| 10000 |
+---------+
1 row in set (0.00 sec)
select count(*) as counter from team;
+---------+
| counter |
+---------+
| 450000 |
+---------+
1 row in set (0.08 sec)
select count(*) as counter from team where athlete_count = 2;
+---------+
| counter |
+---------+
| 112644 |
+---------+
1 row in set (0.03 sec)
select count(*) as counter from team_athlete;
+---------+
| counter |
+---------+
| 1124772 |
+---------+
1 row in set (0.21 sec)
explain
select
p1.person_id as p1_person_id,
p1.person_name as p1_person_name,
p2.person_id as p2_person_id,
p2.person_name as p2_person_name,
count(*) as counter
from
teams_with_2_players_view p1
inner join teams_with_2_players_view p2 on
p2.team_id = p1.team_id and p2.person_id > p1.person_id
group by
p1.person_id, p2.person_id
order by
counter desc
limit 10;
+----+-------------+-------+--------+---------------------+-------------+---------+---------------------+-------+----------------------------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+-------+--------+---------------------+-------------+---------+---------------------+-------+----------------------------------------------+
| 1 | SIMPLE | t | ref | PRIMARY,t_count_idx | t_count_idx | 2 | const | 86588 | Using index; Using temporary; Using filesort |
| 1 | SIMPLE | t | eq_ref | PRIMARY,t_count_idx | PRIMARY | 4 | foo_db.t.team_id | 1 | Using where |
| 1 | SIMPLE | ta | ref | PRIMARY,person | PRIMARY | 4 | foo_db.t.team_id | 1 | Using index |
| 1 | SIMPLE | p | eq_ref | PRIMARY | PRIMARY | 4 | foo_db.ta.person_id | 1 | |
| 1 | SIMPLE | ta | ref | PRIMARY,person | PRIMARY | 4 | foo_db.t.team_id | 1 | Using where; Using index |
| 1 | SIMPLE | p | eq_ref | PRIMARY | PRIMARY | 4 | foo_db.ta.person_id | 1 | |
+----+-------------+-------+--------+---------------------+-------------+---------+---------------------+-------+----------------------------------------------+
6 rows in set (0.00 sec)
select
p1.person_id as p1_person_id,
p1.person_name as p1_person_name,
p2.person_id as p2_person_id,
p2.person_name as p2_person_name,
count(*) as counter
from
teams_with_2_players_view p1
inner join teams_with_2_players_view p2 on
p2.team_id = p1.team_id and p2.person_id > p1.person_id
group by
p1.person_id, p2.person_id
order by
counter desc
limit 10;
+--------------+----------------+--------------+----------------+---------+
| p1_person_id | p1_person_name | p2_person_id | p2_person_name | counter |
+--------------+----------------+--------------+----------------+---------+
| 221 | person 221 | 739 | person 739 | 5 |
| 129 | person 129 | 249 | person 249 | 5 |
| 874 | person 874 | 877 | person 877 | 4 |
| 717 | person 717 | 949 | person 949 | 4 |
| 395 | person 395 | 976 | person 976 | 4 |
| 415 | person 415 | 828 | person 828 | 4 |
| 287 | person 287 | 470 | person 470 | 4 |
| 455 | person 455 | 860 | person 860 | 4 |
| 13 | person 13 | 29 | person 29 | 4 |
| 1 | person 1 | 743 | person 743 | 4 |
+--------------+----------------+--------------+----------------+---------+
10 rows in set (2.02 sec)
インデックス作成は役に立ちますか？ – Sudantha
実際、すべてが適切にインデックスされています。問題は、データベースに数十万行（人：10k、チーム：450k、アスリート：900k）が含まれていることです。 – Anax
サブクエリにジョイン句がない - サブクエリにチームテーブルとアスリートテーブルの両方が必要ですか？ –