帶有最新記錄的嵌套查詢

Question

我正在研究SQL Server 2008數據庫。我需要獲得客戶的特定訂單以及他們的最新訂單ID和最新訂單數據。我的挑戰在於，我需要一行中的數據。目前，我想下面的查詢：

SELECT 
    o.*, 
    c.[FirstName], 
    c.[LastName], 
    c.[PlayerName], 
    (SELECT TOP 1 o2.CreatedDate, o2.ID FROM [Order] o2 ORDER BY [CreatedOn] DESC) 
FROM 
    [Order] o, 
    [Customer] c 
WHERE 
    o.[ID]=c.[CustomerID] 

當我執行此查詢，我得到以下錯誤：

Only one expression can be specified in the select list when the subquery is not introduced with EXISTS. 

正如你可以想像，有場景，其中一個客戶不會有先前的訂單。我如何做到這一點，並得到結果成一行？

謝謝！

Answer 1

使用CTE做一些稍微不同的方法。

WITH LatestOrder AS (SELECT TOP 1 * FROM [Order] ORDER BY [CreatedOn] DESC) 
SELECT 
    o.*, 
    c.[FirstName], 
    c.[LastName], 
    c.[PlayerName], 
    lo.CreatedDate, 
    lo.ID 
FROM [Order] o 
JOIN [Customer] c 
    ON o.[ID]=c.[CustomerID] 
CROSS JOIN LatestOrder lo 

Answer 2

SELECT 
    o.*, 
    c.[FirstName], 
    c.[LastName], 
    c.[PlayerName], 
    (SELECT TOP 1 o2.CreatedDate FROM [Order] o2 ORDER BY [CreatedOn] DESC), 
    (SELECT TOP 1 o2.ID FROM [Order] o2 ORDER BY [CreatedOn] DESC) 
FROM 
    [Order] o, 
    [Customer] c 
WHERE 
    o.[ID]=c.[CustomerID] 

錯誤是說你不能在你的子查詢中選擇兩個字段。所以你必須分開做。