SQL Server：触发器如何读取插入、更新、删除的值

我在一张表中有触发器并且想阅读UserId插入、更新或删除行时的值。怎么做？下面的代码不起作用，我收到错误UPDATED

ALTER TRIGGER [dbo].[UpdateUserCreditsLeft] 
   ON  [dbo].[Order]
   AFTER INSERT,UPDATE,DELETE
AS 
BEGIN
    -- SET NOCOUNT ON added to prevent extra result sets from
    -- interfering with SELECT statements.
    SET NOCOUNT ON;

    DECLARE 
    @UserId INT,

    SELECT @UserId = INSERTED.UserId FROM INSERTED, DELETED

    UPDATE dbo.[User] SET CreditsLeft = CreditsLeft - 1 WHERE Id = @UserId
END

请注意inserted, deleted意思是一样的inserted CROSS JOIN deleted并给出每一行的每种组合。我怀疑这就是你想要的。

像这样的事情可能会帮助你开始......

SELECT
  CASE WHEN inserted.primaryKey IS NULL THEN 'This is a delete'
       WHEN  deleted.primaryKey IS NULL THEN 'This is an insert'
                                        ELSE 'This is an update'
  END  as Action,
  *
FROM
  inserted
FULL OUTER JOIN
  deleted
    ON inserted.primaryKey = deleted.primaryKey

根据您想要执行的操作，然后引用您感兴趣的表inserted.userID or deleted.userID, etc.

最后，请注意inserted and deleted are tables并且可以（并且确实）包含多个记录。

如果一次插入10条记录，inserted表将包含全部 10 条记录。这同样适用于删除和deleted桌子。并且两个表都在更新的情况下。

EDITOP 编辑​​后触发示例。

ALTER TRIGGER [dbo].[UpdateUserCreditsLeft] 
  ON  [dbo].[Order]
  AFTER INSERT,UPDATE,DELETE
AS 
BEGIN

  -- SET NOCOUNT ON added to prevent extra result sets from
  -- interfering with SELECT statements.
  SET NOCOUNT ON;

  UPDATE
    User
  SET
    CreditsLeft = CASE WHEN inserted.UserID IS NULL THEN <new value for a  DELETE>
                       WHEN  deleted.UserID IS NULL THEN <new value for an INSERT>
                                                    ELSE <new value for an UPDATE>
                  END
  FROM
    User
  INNER JOIN
    (
      inserted
    FULL OUTER JOIN
      deleted
        ON inserted.UserID = deleted.UserID  -- This assumes UserID is the PK on UpdateUserCreditsLeft
    )
      ON User.UserID = COALESCE(inserted.UserID, deleted.UserID)

END

如果主键为UpdateUserCreditsLeft是 UserID 以外的其他内容，请在 FULL OUTER JOIN 中使用它。