如何用postgresql按计数排序？

Question

我有两张桌子:

Companies: (id, name, city)
Workers: (id, name)

我想让所有公司按照雇员人数排序.

结果应该给:

count | company id | company name | city
------------------------------------------
90         6           foo corp      NY
45         9           bar corp      LA
0          3         foobar corp     HO

我试过了:

select 
    c.*, 
    count(w.id) as c 
from 
    companies c 
left join 
    workers w 
on 
    c.id = w.company_id 
group by 
    c.id 
order by 
    c desc;

但这不起作用,因为它告诉我也按g.name分组:/

有任何想法吗？

Answer 1

你把表和列别名化为同一个东西,所以不要这样做.它并非无效,只是很难遵循.

无论如何,包括您选择的所有不在您的聚合中的列group by:

select 
    count(w.id) as mycount,
    w.company_id,
    c.company_name,
    c.city
from 
    companies c 
    left join workers w on 
        c.id=w.company_id 
group by 
    w.company_id,
    c.company_name,
    c.city
order by mycount desc;

Answer 2

如果您不希望返回计数结果（由于 ORM 框架左右），您可以直接在 order by 子句中应用它：

select 
    c.*
from 
    companies c 
left join 
    workers w 
on 
    c.id = w.company_id 
group by 
    c.id 
order by 
    count(w.id) desc;

使用 postgreSQL 11 测试