2つのテーブルから引き出されたネストされたSQL文

Question

2つのテーブルからデータを取得しようとしているSQL文に、first_assistと2nd_assistの行であるplayer_idの行を数え、それに応じて3列で表示しようとしています。

ここに私のコードです。

SELECT 

    last_name, 

    (SELECT COUNT (*) FROM goals WHERE player_id = 4 OR player_id = 5) 
    AS player_goals, 

    (SELECT COUNT (*) FROM goals WHERE 1st_assist = 4 OR 1st_assist = 5) 
    AS 1st_assists, 

    (SELECT COUNT (*) FROM goals WHERE 2nd_assist = 4 OR 2nd_assist = 5) 
    AS 2nd_assists 

FROM people 

WHERE player_id = 4 OR player_id = 5 

GROUP BY player_id 

Answer 1

これを試してみてください：

テスト済み

SELECT 
    p.last_name, 
    COUNT(DISTINCT g.id) AS player_goals, 
    COUNT(DISTINCT a1.id) AS 1st_assists, 
    COUNT(DISTINCT a2.id) AS 2nd_assists 
FROM 
    people p 
    LEFT JOIN goals g ON (g.player_id = p.player_id) 
    LEFT JOIN goals a1 ON (a1.1st_assist = p.player_id) 
    LEFT JOIN goals a2 ON (a2.2nd_assist = p.player_id) 
WHERE 
    p.player_id = 4 OR p.player_id = 5 
GROUP BY p.player_id 

：

mysql> select * from people; 
+-----------+-----------+------------+ 
| player_id | last_name | first_name | 
+-----------+-----------+------------+ 
|   4 | Francis | Jeff  | 
|   5 | Doe  | John  | 
|   6 | Barratt | Glen  | 
+-----------+-----------+------------+ 
3 rows in set (0.00 sec) 

mysql> select * from goals; 
+----+-----------+------------+------------+---------------------+ 
| id | player_id | 1st_assist | 2nd_assist | when_made   | 
+----+-----------+------------+------------+---------------------+ 
| 1 |   4 |   6 |   5 | 2011-11-07 15:05:31 | 
| 2 |   4 |   5 |  NULL | 2011-11-07 15:05:37 | 
| 3 |   5 |   4 |   6 | 2011-11-07 15:05:45 | 
| 4 |   6 |   4 |   5 | 2011-11-07 15:05:52 | 
| 5 |   4 |   6 |  NULL | 2011-11-07 15:06:05 | 
| 6 |   5 |  NULL |  NULL | 2011-11-07 15:06:15 | 
| 7 |   6 |   4 |  NULL | 2011-11-07 15:06:21 | 
| 8 |   5 |   6 |  NULL | 2011-11-07 15:06:31 | 
| 9 |   4 |  NULL |  NULL | 2011-11-07 15:15:21 | 
| 10 |   4 |   6 |  NULL | 2011-11-07 15:15:27 | 
| 11 |   6 |   5 |   4 | 2011-11-07 15:15:38 | 
+----+-----------+------------+------------+---------------------+ 
11 rows in set (0.00 sec) 

mysql> SELECT p.last_name, COUNT(DISTINCT g.id) AS player_goals, COUNT(DISTINCT a1.id) AS 1st_assists, COUNT(DISTINCT a2.id) AS 2nd_assists FROM people p LEFT JOIN goals g ON (g.player_id = p.player_id) LEFT JOIN goals a1 ON (a1.1st_assist = p.player_id) LEFT JOIN goals a2 ON (a2.2nd_assist = p.player_id) WHERE p.player_id = 4 OR p.player_id = 5 GROUP BY p.player_id; 
+-----------+--------------+-------------+-------------+ 
| last_name | player_goals | 1st_assists | 2nd_assists | 
+-----------+--------------+-------------+-------------+ 
| Francis |   5 |   3 |   1 | 
| Doe  |   3 |   2 |   2 | 
+-----------+--------------+-------------+-------------+ 
2 rows in set (0.00 sec)