mysql - 单个 sql 中有多个 count* sql

Question

我想将这些 sql 语句用作单个语句，这将导致具有不同计数和 company_id 的 4 列。

select company_id,count(*) as det from feedbacks a join( select id,company_id from users  ) b on a.user_id = b.id where healthi_rating < 7 group by company_id
select company_id,count(*) as neu from feedbacks a join( select id,company_id from users  ) b on a.user_id = b.id where healthi_rating <9 && healthi_rating >=7 group by company_id
select company_id,count(*) as pro from feedbacks a join( select id,company_id from users  ) b on a.user_id = b.id where healthi_rating >=9 group by company_id

谁能告诉我怎么做。

Answer 1

对于 MySQL 做

select company_id,
       sum(healthi_rating < 7) as det,
       sum(healthi_rating between 7 and 8) as neu,
       sum(healthi_rating >= 9) as pro
from feedbacks a 
join( select id, company_id from users ) b on a.user_id = b.id 
group by company_id

并使用 ANSI SQL 标准且没有 users 的子查询

select b.company_id,
       sum(case when healthi_rating < 7 then 1 else 0 end) as det,
       sum(case when healthi_rating between 7 and 8 then 1 else 0 end) as neu,
       sum(case when healthi_rating >=9 then 1 else 0 end) as pro
from feedbacks a 
join users b on a.user_id = b.id 
group by b.company_id