mysql - 如何在同一张桌子上加入两个选择

Question

我有两个选择语句，例如

Select author_id, count(text) from posts group by author_id

select author_id, count(text) from posts where postcounter =1 group by author_id

有没有办法在一个查询中组合这两个语句？结果长度不同，因此需要在第二个结果集中插入一些 0。

非常感谢您的帮助

最好的问候，西蒙娜

Answer 1

这是你要找的吗？

select author_id, 
   sum(case when postcounter = 1 then 1 else 0 end) count1, 
   sum(case when postcounter <> 1 then 1 else 0 end) count2,
   count(text) allcount
from posts  
group by author_id

Answer 2

您应该能够在单个查询中使用：

Select author_id, 
  count(text) TextCount,
  count(case when postcounter=1 then text end) PostCount
from posts 
group by author_id

Answer 3

您可以尝试使用 union all 语句吗？

   SELECT `id`,sum(`count`) FROM (
Select  author_id as `id`, count(text) as `count` from posts group by author_id 
UNION ALL 
select author_id as `id`, count(text) as `count` from posts where postcounter =1 group by author_id
    )