使用与左where子句加入

Question

我有这两个表：

USER: 
id name 
1 John 
2 Cian 
3 Una 

ATTR: 
id name   value  user_id 
1 LAST_LOGGED_IN 2016-10-10 1 
1 ADDED   2015-01-01 1 
1 ADDED   2015-01-01 2 

，并希望产生这样的：

user_id user_name last_logged_in added 
1  John  2016-10-10  2015-01-01 
2  Cian  NULL   2015-01-01 
3  Una  NULL   NULL 

我的尝试是：

select USER.NAME, ATTR.VALUE as LAST_LOGGED_IN 
from USER 
left join ATTR on USER.ID = ATTR.USER_ID 
where ATTR.NAME = "LAST_LOGGED_IN" 
GROUP BY USER.NAME; 

但是不正确的。

Answer 1

select USER.NAME, IF(ATTR.NAME = 'LAST_LOGGED_IN',ATTR.VALUE,NULL) as LAST_LOGIN 
from USER 
right join ATTR on USER.ID = ATTR.USER_ID 
GROUP BY USER.ID;