SQL Server：如何在單個查詢中執行 2 個選擇語句

Question

我想先計算列：作為每列的實例總數，第二個根據條件計算實例總數。

我正在使用這個：

SELECT
    group_name,
    Definition_Range,
    COUNT([group_name]) AS Number_of_Clients
FROM 
    [Computer Status]
WHERE
    Definition_Range = ' 0-10 Days'
GROUP BY
    group_name,
    (SELECT COUNT([group_name]) AS Total_Clients
     FROM [Computer Status]
     GROUP BY group_name)

Answer 1

以下查詢沒有意義

SELECT COUNT([group_name]) AS Total_Clients
         FROM [Computer Status]
         GROUP BY group_name

它返回與主查詢中寫入的Number_of_Clients相同。 因為您正在group by group_name進行group by 。

下面是完美的查詢

   SELECT
        group_name,
        Definition_Range,
        COUNT([group_name]) AS Number_of_Clients
    FROM 
        [Computer Status]
    WHERE
        Definition_Range = ' 0-10 Days'
    GROUP BY
        group_name,Definition_Range