mysql - sql query regarding favorited authors of each user

Question

We have two tables.

1. information

title    body     name   

title1   body1   author1   
title2   body2   author1    
title1   body1  author2 
title1   body1   author3

2. interactions

name      favorited    user_favorited_by

author1      yes          user1 
author2      yes          user1 
author1      yes          user2 
author1      no          user3

The question is: who is for each user the favourite author or authors?

The query should give us the following answer based on the example:

user1    author1
user1    author2
user2    author1

Any help appreciated.

Answer 1

这是一个有效的 JOIN：

SELECT DISTINCT user_favorited_by,   a.name
  FROM information a
  JOIN interactions b
  ON a.name = b.name
 WHERE  favorited = 'yes'

由于您只有“名称”可以加入，因此您需要 DISTINCT，或者您可以按所选字段分组以从输出中删除重复行。

这是一个演示： SQL Fiddle

Answer 2

我可以建议：

select user_favorited_by, author from information a
inner join interaction b on a.name = b.name 
where b.favorited = 'yes'

Answer 3

我认为以下应该有效

SELECT DISTINCT user_favorited_by,
                a.name
  FROM information a,
       interactions b
 WHERE a.name = b.name
   AND favorited = 'yes'