如何从两列中获取 2 个 id 并从另一个表中获取所有记录

Question

I have tow table as below 

FWTable

mid uname   gender  avatar          email           psw     dob         city
1   User 1  Male    cat.jpg         user1@gmail.com psw1    2015-05-18  Ahmedabad
2   User 2  Female  Koala.jpg       user2@gmail.com psw2    2015-05-15  Jamnagar
3   User 3  Male    Desert.jpg      user3@gmail.com psw3    2015-04-25  Porbandar
4   User 4  Female  Jellyfish.jpg   user4@gmail.com psw4    2015-06-11  Jamnagar
5   User 5  Male    Penguins.jpg    user5@gmail.com psw5    2015-07-10  Jamnagar
6   User 6  Female                  user6@gmail.com psw6    2015-05-12  Jamnagar

好友列表

fid     mid friend_id   friend_status
1       1   2           1
2       1   3           0
3       2   4           0
1002    3   4           1
1003    5   1           1

当用户1(mid 1)在线时，我想显示那些朋友喜欢的。

2   User 2  Female  Koala.jpg       user2@gmail.com psw2    2015-05-15  Jamnagar
5   User 5  Male    Penguins.jpg    user5@gmail.com psw5    2015-07-10  Jamnagar

Answer 1

试试这个：

select t1.*
from FWTable t1
join FriendsList t2 on t1.mid = t2.mid
where t2.friend_id = 1
and status = 1

union

select t1.*
from FWTable t1
join FriendsList t2 on t1.mid = t2.friend_id
where t2.mid = 1
and status = 1

Answer 2

with all_friendships as (
    --making a distinct list of all friendships, for both directions
    select mid as the_user, friend_id as the_friend 
        from FriendsList 
        where friend_status = 1
    union
    select friend_id as the_user, mid as the_friend 
        from FriendsList 
        where friend_status = 1
)

select mid, uname, gender, avatar, email, psw, dob, city
from all_friendships
inner join FWTable on the_friend = mid
where the_user = 1

看起来你想展示双向的友谊，不仅是 mid 1 的朋友，还有 mid 1 的朋友。这应该可以解决这个问题。