SQL Server：WHERE子句中的CASE

Question

我需要創建一個SQL語句來檢查條件，如果該列為null，它將執行其他條件。 以下是我的示例：

SELECT  
    REPLACE(xxShip.Shipment_Date, '/', '-') AS ShipDate,xxShip.Customer,
    xxShip.TravelSheetNo
FROM 
    (SELECT 
         RANK() OVER (PARTITION BY TravelSheetNo ORDER BY created_on DESC) AS shipwocode,
         ShipDate, ShipTime, Shipment_Date, 
         Customer, Product_no, TravelSheetNo,
         [status], ProcessLotNo
     FROM  
         xxDEShipment) xxShip
WHERE 
    xxShip.shipwocode = 1
    AND xxShip.TravelSheetNo = 'ABC'
    --here i need to check the condition----------------------------
    AND (CASE 
            WHEN ISNULL(xxShip.Shipment_Date,'') != '' OR xxShip.Shipment_Date != '' 
              THEN
                 xxShip.Shipment_Date IS NULL OR xxShip.Shipment_Date = '' 
              ELSE
                 CONVERT(DATETIME, xxShip.Shipment_Date) >=  @DATESTART and CONVERT(DATETIME, xxShip.Shipment_Date) <=  @DATEEND
         END)

請幫忙。 謝謝

Answer 1

這應該是這樣的：

AND(
     (ISNULL(xxShip.Shipment_Date,'') <> '' AND 
      CONVERT(DATETIME, xxShip.Shipment_Date) >=  @DATESTART AND 
      CONVERT(DATETIME, xxShip.Shipment_Date) <=  @DATEEND
     ) 
     OR ISNULL(xxShip.Shipment_Date,'') == ''
   )

請注意，將日期存儲為字符串是一種不好的做法。

Answer 2

如果您需要選擇@DATESTART和@DATEEND之間的日期， 或者為空或空日期，請使用以下方法：

ISNULL(CONVERT(DATETIME, NULLIF(xxShip.Shipment_Date, '')), @DATESTART) 
    BETWEEN @DATESTART AND @DATEEND