使用帶左連接的where子句

Question

我有這兩個表：

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

並希望產生這個：

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

我的嘗試是：

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;

但這是不正確的。

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;