SQL - 使用触发器偶尔允许删除行

Question

我有一些正在使用的视图，如果数据表被另一个表中的变量锁定，我需要设置一个触发器来防止删除视图中的任何数据。我已经设置了触发器，并且使用“INSTEAD OF DELETE”触发器设置删除命令的替换没有问题，但我现在的问题是如何在删除时保留传入的删除查询 是允许的。在本例中，我使用的是 SQL Server。

例如，如果控制表说我的视图被锁定，那么任何发送到数据库的删除查询都应该停止，并且应该返回错误消息（这里没有问题，已经有了）。但是，如果控制表显示我的视图已解锁，我需要能够允许删除查询从视图中删除数据（这里我需要帮助）。

代码：

CREATE TRIGGER [database_name].[trigger_name]
ON [database_name].[view_name]
INSTEAD OF DELETE
AS
BEGIN
    SET NOCOUNT ON

    IF NOT EXISTS (SELECT * FROM [database_name].[control_table_name]
                   WHERE Control_Item = 'view_name' AND Can_modify = 'N')
    BEGIN
        SET NOCOUNT OFF
        --NEW DELETION STATEMENT GOES HERE, NEEDS TO BE DUPLICATE OF REPLACED DELETE QUERY--
    END
    ELSE
    BEGIN
        RAISEERROR('Deletions are currently disabled!', 11, 1);
    END
END

我确定有一些愚蠢的逻辑陈述或我遗漏的东西，但我会感谢我能得到的所有帮助。谢谢！

Answer 1

您不能直接从视图中删除 - 您需要从基础表中删除。

所以基本上，您需要为您的表添加一个（或多个）DELETE 语句 - 希望您已将所有基础表的主键包含到您的视图中！

CREATE TRIGGER [database_name].[trigger_name]
ON [database_name].[view_name]
INSTEAD OF DELETE
AS
BEGIN
    SET NOCOUNT ON

    IF NOT EXISTS (SELECT * FROM [database_name].[control_table_name]
                   WHERE Control_Item = 'view_name' AND Can_modify = 'N')
    BEGIN
        SET NOCOUNT OFF

        DELETE FROM dbo.YourFirstTable
        WHERE PrimaryKeyColumn IN (SELECT FirstPrimaryKeyColumn FROM Deleted);

        -- if the view is built on top of several tables, you possibly need multiple DELETE statements here
        DELETE FROM dbo.YourSecondTable
        WHERE PrimaryKeyColumn IN (SELECT SecondPrimaryKeyColumn FROM Deleted);
    END
    ELSE
    BEGIN
        RAISEERROR('Deletions are currently disabled!', 11, 1);
    END
END

Answer 2

也许“FOR DELETE”可以解决问题，并在不允许删除时进行回滚。

CREATE TRIGGER [database_name].[trigger_name] 
ON [database_name].[view_name]
FOR DELETE
AS
    SET NOCOUNT ON

    IF EXISTS (SELECT * 
               FROM [database_name].[control_table_name]
               WHERE Control_Item = 'view_name' AND Can_modify = 'N')
    BEGIN
        RAISEERROR('Deletions are currently disabled!', 11, 1) WITH NOWAIT
        ROLLBACK
    END

    SET NOCOUNT OFF
GO