加入3代表與MySQL返回額外數據

Question

我有3個表 - 會員，活動，新

成員表：

+--------+---------+------------+ 
| userid | adminid | logindate | 
+--------+---------+------------+ 
| test6 | test3 | 03/04/2016 | 
| test7 | test3 |   | 
+--------+---------+------------+ 

活動表：

+----+--------+---------+---------+ 
| id | userid | adminid | city | 
+----+--------+---------+---------+ 
| 1 | test6 | test3 | Chicago | 
+----+--------+---------+---------+ 

新表：

+----+--------+----------+ 
| id | userid | city  | 
+----+--------+----------+ 
| 1 | test7 | New York | 
+----+--------+----------+ 

我想找出所有的memb屬於管理員標識（test3）的ers，無論它們是主動還是新的。 MySQL的代碼：

SELECT active.id, active.userid, active.city, members.logindate, 
new.id as a, new.userid as b, new.city as c 
    FROM members 
    LEFT JOIN active 
    ON members.adminid = active.adminid 
    LEFT JOIN new 
    ON members.userid = new.userid 
    WHERE members.adminid = 'test3' 

我希望會是2行的記錄：

+----+--------+---------+------------+---+-------+----------+ 
| id | userid | city | logindate | a | b | c  | 
+----+--------+---------+------------+---+-------+----------+ 
| 1 |test6 | Chicago | 03/04/2016 | |  |   | 
+----+--------+---------+------------+---+-------+----------+ 
| |  |   |   | 1 | test7 | New York | 
+----+--------+---------+------------+---+-------+----------+ 

相反，我得到了：

+----+--------+---------+------------+---+-------+----------+ 
| id | userid | city | logindate | a | b | c  | 
+----+--------+---------+------------+---+-------+----------+ 
| 1 |test6 | Chicago | 03/04/2016 | |  |   | 
+----+--------+---------+------------+---+-------+----------+ 
| 1 |test6 | Chicago |   | 1 | test7 | New York | 
+----+--------+---------+------------+---+-------+----------+ 

從第一行中的數據（從活動表）在第二行重複。我究竟做錯了什麼？感謝您的幫助。提前致謝。

Answer 1

您應該join在userid而不是adminid：

SELECT active.id, active.userid, active.city, members.logindate, 
    new.id as a, new.userid as b, new.city as c 
FROM members 
    LEFT JOIN active 
     ON members.userid = active.userid 
    LEFT JOIN new 
     ON members.userid = new.userid 
WHERE members.adminid = 'test3' 

• Condensed Fiddle Demo