使用 MySQL 中同一个表的 COUNT 连接两个查询

Question

我在同一个表中运行了两个查询：

SELECT id, COUNT(up) 
FROM comentarios 
WHERE up = 1
GROUP BY id

我

SELECT id, COUNT(down) 
FROM comentarios 
WHERE down = 2
GROUP BY id

尝试了类似的操作，但不起作用

SELECT t1.id, COUNT(t1.up), t2.id, COUNT(t2.down)
FROM (SELECT id, up FROM comentarios WHERE up = 1 GROUP BY id) t1
JOIN (SELECT id, down FROM comentarios WHERE down = 2 GROUP BY id) t2

ON t1.id = t2.id

也许需要完整的外部连接？

在 MySQL 中执行此操作的最佳方法是什么？

Answer 1

SELECT id,
       SUM(CASE WHEN up = 1 THEN 1 ELSE 0 END) AS UpCount,
       SUM(CASE WHEN down = 2 THEN 1 ELSE 0 END) AS DownCount
    FROM comentarios
    GROUP BY id

Answer 2

select id, 
    sum(case when up = 1 then 1 end) as UpCount,
    sum(case when down = 2 then 1 end) as DownCount
from comentarios  
group by id