Question

select distinct hash, title, count(*) as c
from pastes 
where hash is not null  
group by hash, title 
order by c desc;

我可以根据我在查询中即时定义的“c”列对此查询的结果进行排序。

但我还想在WHERE子句中添加c：

select distinct hash, title, count(*) as c 
from pastes 
where c > 10 and hash is not null  
group by hash, title 
order by c desc;

ERROR:  column "c" does not exist
LINE 1: ...inct hash, title, count(*) as c from pastes where c > 10 and...
                                                             ^

指定这样的查询的正确方法是什么？

Answer 1

使用having

完成聚合的条件

select hash, title, count(*) as c 
from pastes 
where hash is not null  
group by hash, title 
having count(*) > 10
order by c desc;

Answer 2

您可以将其包装为子查询：

select q.* from (
select hash, title, count(*) as c 
from pastes where hash is not null  
group by hash, title 
) q
where q.c > 10 
order by q.c desc;

您可以跳过子查询并使用HAVING而不是WHERE，但我发现您还需要ORDER BY c，因此子查询。

如何在我的WHERE子句

2 个答案: