問題上的MySQL INNER JOIN

Question

我想下面的查詢顯示所有我在用戶頁面的用戶的...

SELECT u.id, u.username, u.email, u.active, u.admin, 
u.team_id, t.name AS team_name, sum(s.score) AS total_score 
FROM users u 
INNER JOIN teams t ON u.team_id = t.id 
INNER JOIN stats s ON u.id = s.user_id 

我有我的用戶表4級的用戶，我想列出所有，但如果我使用INNER JOIN，它只返回1行。檢查數據結構如下...

| id | game | user_id | rank | score | dnt | 
+----+------+---------+-------+------+-----+ 
| 1 | test | 5  | 2 | 2200 | 
+--------+----------+----------+-----+-----+ 
| 2 | test | 3  | 1 | 2500 | 
+--------+----------+----------+-----+-----+ 

隊

| id | name | dnt | 
+----+-------+-----+ 
| 1 | team1 |  | 
+----+-------+-----+ 
| 2 | team2 |  | 
+----+-------+-----+ 

用戶

| id | username | email | team_id | 
+----+----------+-------+---------+ 
| 1 | user1 |  | 1  | 
+----+----------+-------+---------+ 
| 1 | user2 |  | 2  | 
+----+----------+-------+---------+ 

Answer 1

你需要使用GROUP BY，以便在不同的用戶分割得分的總和，進一步，如果你使用LEFT JOIN，那麼即使在stats表中沒有行，您也一定會爲每個用戶實例獲得一行（然後，使用COALESCE作爲regilero建議的，總和將0）

類似：

SELECT u.id, u.username, u.email, u.active, u.admin, 
u.team_id, t.name AS team_name, sum(COALESCE(s.score)) AS total_score 
FROM users u 
LEFT JOIN teams t ON u.team_id = t.id 
LEFT JOIN stats s ON u.id = s.user_id 
GROUP BY u.id, u.username, u.email, u.active, u.admin, 
u.team_id, t.name 

這不是測試