使用查询结果向结果中添加另一列 SQL

Question

These are the relevant tables:

• userInfo

  • username
  • profileImgUrl

• follows

  • follower
  • following

In the follows table the follower and the following attributes are usernames. Where the follower follows the following.

I would like to add another column where it states if the person requesting the query, in this case, 'admin', follows the selected u.username.

Current query:

SELECT u.username, u.profileImgUrl 
FROM userInfo u, follows f WHERE f.following = 'admin'
AND f.follower = u.username

Answer 1

I think you want:

select u.*,
       ( exists (select 1 from follows f where f.follower = u.username and f.following = 'admin')
       ) as flag
from userInfo u;

MySQL supports a "boolean" data type that can look a lot like a number, so this returns "1" if a row exists in followers and 0 if it does not.