mysql - 计数不正确

Question

我有一个表格来计算一个用户的评论和喜欢:

http://sqlfiddle.com/#!9/5cda66/1

有 3 个赞和 6 个评论。但它显示了 3 个赞和 18 个评论。它总是在成倍增加。 3 x 6 = 18，这是错误的。

如何解决？

select 

count(DISTINCT likes.user) as likes_count,
SUM(CASE comentarios.delete WHEN 0 THEN 1 ELSE 0 END) as comentarios_count 

from posts p

left join likes on likes.post = p.id
left join comentarios on comentarios.foto = p.id

group by p.id

Answer 1

如果将条件放在 left join 子句中，您还可以在注释中使用 count(distinct)

select count(distinct l.user) as likes_count,
       count(distinct c.id) as comentarios_count     
from posts p    
left join likes l on l.post = p.id
left join comentarios c on c.foto = p.id
                       and c.delete = 0    
group by p.id

SQLFiddle demo