合并 - 条件“匹配时更新”

下图中的亮点显示了我想要实现的逻辑。我意识到语法不正确。

有没有办法有条件地更新 MERGE 语句中的记录，仅当目标表中某一列的值为 NULL，并且源表中相应的值不为 null 时？

你建议如何重写这个？

MERGE dbo.input_311 AS [t]
USING dbo.input_311_staging AS [s]
ON ([t].[unique key] = [s].[unique key])
WHEN NOT MATCHED BY TARGET
    THEN INSERT(t.[Created Date]) VALUES(s.[Created Date])
WHEN MATCHED
    THEN UPDATE SET(t.[Created Date] = s.[Created Date]
                WHERE s.[Created Date] IS NOT NULL
                AND t.[Created Date] IS NULL)
OUTPUT deleted.*, $action, inserted.*;
GO

你也许可以使用When Matched And (s.[Created Date] Is Not Null And t.[Created Date] Is Null) Then Update ....