SELECT中的case語句

Question

ALTER PROCEDURE Transform.usp_CustomerInfo
AS
BEGIN
    TRUNCATE TABLE [Transform].[CustomerInfo]

    INSERT INTO [Transform].[CustomerInfo] (CustomerName, Total, AvgPurchaseTime, StoreName)
        SELECT
            CASE
               WHEN C.LastName = NULL THEN C.FirstName
               ELSE (C.LastName + ', ' + C.FirstName)
            END AS 'Name', 
            SUM(T.Total),
            D.FullDate,
            UPPER(C.StoreName) AS 'Store Name'
        FROM 
            [Extract].[DimTransaction] AS T
        JOIN 
            [Extract].[DimCustomer] AS C ON T.CustomerID = C.CustomerID
        JOIN 
            [Extract].[DimState] AS S ON C.StateID = S.StateID
        JOIN 
            [Extract].[DimDateTime] AS D ON D.DateTimeID = T.TransactionID
        GROUP BY 
            C.LastName, C.FirstName, D.FullDate, C.StoreName
        ORDER BY 
            Convert(date, D.FullDate, 101) ASC

我試圖得到它，如果姓氏出現NULL只使用第一個名稱，否則我想連接姓氏和名字

Answer 1

你可以這樣寫：

(CASE WHEN C.LastName IS NULL THEN C.FirstName
      ELSE (C.LastName + ', ' + C.FirstName)
 END) AS Name, 

或者只使用COALESCE() ：

(COALESE(C.LastName + ', ', '') + C.FirstName) as Name

Answer 2

NULL不是值，因此不能使用=，<，>與其他值進行比較。 BTW，你的情況何時聲明也可以用ISNULL

ISNULL(C.LastName + ', ','')+c.FirstName AS Name

Answer 3

您不能檢查為= NULL，但您可以通過以下方式檢查默認值，或者您必須采用其他人建議的方式：

CASE WHEN ISNULL(c.lastName,'') = '' THEN 
    -------
ELSE
    -------
END

如果您使用的是SQLSERVER2008 +，那么您也可以使用CONCAT：

CONCAT(ISNULL(c.lastname + ', ',''), c.firstname) as Name