¿Cómo uso Count (*) en una declaración Where?

Question

No entiendo por qué esto no funciona y cómo solucionarlo, probé varias cosas como escribir

select COUNT(p.OwnerUserId)

Pero eso no funciona y no entiendo los mensajes de error. No uso MS SQL (uso SQLite y MySQL).

¿Cómo escribo esta consulta para poder filtrar el QC por 10 o 50? (Donde QC> 50 y ...)

Básicamente, conecte el SQL a continuación en esta URL, ejecutela y verá 1 en los resultados.http://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

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 ) between 10 and 50   -- <<<<<
order by AVC desc

Otra opción es convertirlo en un subconsulto

SELECT
    TOP 100
FROM (
SELECT
    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
) SQ
WHERE QC >= 50
order by AVC desc

Answer 2

Debe usar la cláusula de tener para filtrar un campo agregado

Prueba esto:

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

Answer 3

Cuando esté utilizando agregados, debe usar having en vez de where.