sql-server - 我如何在 where 语句中使用 Count(*)？

Question

我不明白为什么这不起作用以及如何解决它，我尝试了各种方法，比如写作

select COUNT(p.OwnerUserId)

但这不起作用，我不明白错误消息。我不使用 MS SQL(我使用 SQLite 和 MySQL)。

我如何编写此查询以便按 10 或 50 筛选 QC？ (其中 QC > 50 和 ...)

基本上将下面的 SQL 插入此 URL，运行它，您将在结果中看到 1。 https://data.stackexchange.com/stackoverflow/query/new

SELECT
    TOP 100
    p.OwnerUserId  AS [User Link],
    sum(ViewCount) as VC,
    avg(ViewCount) as AVC,
    COUNT(p.OwnerUserId ) as QC

FROM Posts p
join Users on p.OwnerUserId = Users.Id
where PostTypeId = 1 and ViewCount<10000 and CommunityOwnedDate is null
group by p.OwnerUserId
order by AVC desc

Answer 1

您需要使用 Having 子句来过滤聚合字段

试试这个:

SELECT
    TOP 100
    p.OwnerUserId  AS [User Link],
    sum(ViewCount) as VC,
    avg(ViewCount) as AVC,
    COUNT(p.OwnerUserId ) as QC

FROM Posts p
join Users on p.OwnerUserId = Users.Id
where PostTypeId = 1 and ViewCount<10000 and CommunityOwnedDate is null
group by p.OwnerUserId  
HAVING COUNT(p.OwnerUserId ) > 50
order by AVC desc