計算select查詢返回的行數

Question

我需要計算以下查詢返回的行數。

select m.Company_id 
from Monitor as m 
    inner join Monitor_Request as mr on mr.Company_ID=m.Company_id 
    group by m.Company_id 
    having COUNT(m.Monitor_id)>=5 

我試圖與以下

select COUNT(*) from 
(
select m.Company_id 
from Monitor as m 
    inner join Monitor_Request as mr on mr.Company_ID=m.Company_id 
    group by m.Company_id 
    having COUNT(m.Monitor_id)>=5) 

它給在查詢分析器的錯誤消息，其表示如下：

消息102，級別15，狀態1，行7不正確的語法靠近'）'。

Answer 1

SQL Server要求的子查詢，你SELECT FROM或JOIN有一個別名。

一個別名添加到您的子查詢（在這種情況下x）：

select COUNT(*) from 
(
select m.Company_id 
from Monitor as m 
    inner join Monitor_Request as mr on mr.Company_ID=m.Company_id 
    group by m.Company_id 
    having COUNT(m.Monitor_id)>=5) x 

Answer 2

select COUNT(*) 
from Monitor as m 
    inner join Monitor_Request as mr on mr.Company_ID=m.Company_id 
    group by m.Company_id 
    having COUNT(m.Monitor_id)>=5 

Answer 3

嘗試包裹整個選擇括號，然後在該

select count(*) 
from 
(
    select m.id 
    from Monitor as m 
    inner join Monitor_Request as mr 
     on mr.Company_ID=m.Company_id group by m.Company_id 
    having COUNT(m.Monitor_id)>=5 
) myNewTable 

Answer 4

語法運行COUNT（*）錯誤只是由於子查詢缺少別名：

select COUNT(*) from 
(
select m.Company_id 
from Monitor as m 
    inner join Monitor_Request as mr on mr.Company_ID=m.Company_id 
    group by m.Company_id 
    having COUNT(m.Monitor_id)>=5) mySubQuery /* Alias */