'CASE WHEN' 更新时，其他列变为空

Question

我在 tmy 数据库中使用用户定义的 table 类型通过数据更新多个列table。

因此，我编写了以下存储过程并且运行良好。但是在更新相应的列时，这会使所有其他列为空。

我的存储过程：

ALTER PROCEDURE [dbo].[UpdateAbcdItemsByVendorPrice]
      @tblItemUpdate AbcdItemsUpdate READONLY
AS
BEGIN
    SET NOCOUNT ON;

    MERGE INTO AbcdItems abcdTable
    USING @tblItemUpdate tempTable
    ON abcdTable.ItemPartNumber = tempTable.ItemPartNumber
    WHEN MATCHED THEN
    UPDATE SET
        abcdTable.InpostPrice = CASE WHEN tempTable.VendorName = 'Inpost' THEN tempTable.Price END,
        abcdTable.InpostUpdatedDate = CASE WHEN tempTable.VendorName = 'Inpost' THEN GETUTCDATE() END,
        abcdTable.InpostAbsoluteItem = CASE WHEN tempTable.VendorName = 'Inpost' THEN 0 END,

        abcdTable.HRCPrice = CASE WHEN tempTable.VendorName = 'HRC' THEN tempTable.Price END,
        abcdTable.HRCUpdatedDate = CASE WHEN tempTable.VendorName = 'HRC' THEN GETUTCDATE() END,
        abcdTable.HRCAbsoluteItem = CASE WHEN tempTable.VendorName = 'HRC' THEN 0 END,

        abcdTable.AnnecyPrice = CASE WHEN tempTable.VendorName = 'Annecy' THEN tempTable.Price END,
        abcdTable.AnnecyUpdatedDate = CASE WHEN tempTable.VendorName = 'Annecy' THEN GETUTCDATE() END,
        abcdTable.AnnecyAbsoluteItem = CASE WHEN tempTable.VendorName = 'Annecy' THEN 0 END,

        abcdTable.SydneyPrice = CASE WHEN tempTable.VendorName = 'Sydney' THEN tempTable.Price END,
        abcdTable.SydneyUpdatedDate = CASE WHEN tempTable.VendorName = 'Sydney' THEN GETUTCDATE() END,
        abcdTable.SydneyAbsoluteItem = CASE WHEN tempTable.VendorName = 'Sydney' THEN 0 END;
END

My table 在为 'Inpost' 执行此查询之前：

InpostPrice    HRCPrice    ...
0              0           ...

我的 table 在为 'Inpost' 执行此查询后：

InpostPrice    HRCPrice    ...
213.57         NULL        ...

为什么HRCPrice 变成了null？抱歉英语不好。帮帮我！

Answer 1

您正在分配 NULL，因为您的 CASE 中没有 ELSE。我假设您想要使用旧值：

UPDATE SET
    abcdTable.InpostPrice = CASE WHEN tempTable.VendorName = 'Inpost'
                             THEN tempTable.Price 
                             ELSE abcdTable.InpostPrice END,
   .....

来自documentation：

ELSE else_result_expression: Is the expression returned if no comparison operation evaluates to TRUE. If this argument is omitted and no comparison operation evaluates to TRUE, CASE returns NULL

Answer 2

您需要在 case 语句中添加 else 部分。

UPDATE SET
        abcdTable.InpostPrice = CASE WHEN tempTable.VendorName = 'Inpost' THEN tempTable.Price 
                                ELSE abcdTable.InpostPrice  END,
        abcdTable.InpostUpdatedDate = CASE WHEN tempTable.VendorName = 'Inpost' THEN GETUTCDATE() 
                                      ELSE abcdTable.InpostUpdatedDate END,
        abcdTable.InpostAbsoluteItem = CASE WHEN tempTable.VendorName = 'Inpost' THEN 0 
                                       ELSE abcdTable.InpostAbsoluteItem END,
......

Answer 3

因为每一列都无条件更新并且您的 case 语句将默认为 null。将当前值作为默认值：

     abcdTable.InpostPrice = CASE WHEN tempTable.VendorName = 'Inpost' THEN tempTable.Price 
else abcdTable.InpostPrice
END,

'CASE WHEN' 更新时，其他列变为空

While 'CASE WHEN' update, other columns become null

sql-server

stored-procedures

case-when