显示条件为 <= 2 的空计数

Question

目前正在尝试查找已确诊 0-2 次的疾病。我能够显示每种疾病被诊断出多少次，包括 0 次，但是当我尝试查看计数为 0-2 的疾病时，我的查询就不起作用了。

这让我得到了计数（包括 0）：

select disease.name, count(diagnosed.diseaseid) as timesdiagnosed
from disease
left join diagnosed on disease.diseaseid = diagnosed.diseaseid
group by disease.name;

此代码无效：

select disease.name, count(diagnosed.diseaseid) as timesdiagnosed
from disease
left join diagnosed on disease.diseaseid = diagnosed.diseaseid
group by disease.name
order by disease.name
having count(diagnosed.diseaseid) <= 2;

我的 RDMBS 是 oracle。

Answer 1

having 子句应位于 order by 之前和 group by 之后：

select disease.name, count(diagnosed.diseaseid) as timesdiagnosed
from disease
left join diagnosed on disease.diseaseid = diagnosed.diseaseid
group by disease.name
having count(diagnosed.diseaseid) <= 2
order by disease.name

显示条件为 <= 2 的空计数

Show null counts with a condition of <= 2

sql

oracle

null

count

left-join