SQL分组依据：使用where子句逻辑基于聚合函数过滤结果

Question

我有一个基本的group by / avg语句：

select url, avg(contentping+tcpping), count(*) from websites ws, ping pi 
where ws.idwebsite = pi.idwebsite and errortype is null
group by url order by avg(contentping+tcpping) asc;

我现在想做的是删除任何比平均ping高500的结果。我该怎么做…？

Answer 1

只需添加一个having子句：

select url, avg(contentping+tcpping), count(*) from websites ws, ping pi 
where ws.idwebsite = pi.idwebsite and errortype is null
group by url 
having avg(contenetping+tcpping) < 500
order by avg(contentping+tcpping) asc;