Question

我认为对于那些使用T-SQL，尤其是触发器工作很多的人来说，这将是一个简单的问题：

我希望对此表的所有更新和插入强制执行以下约束：

如果DiscountTypeId = 1，则FlatFee不得为NULL。
如果DiscountTypeId = 2，则DiscountRate不得为空。

如果在插入或更新表中这两个条件中的任何一个失败，我想返回一个适当的错误。

触发器似乎还没有做任何事情。。您可以提供必要的更改，使其按照描述执行吗？

USE [PandaVisa2008]
GO

/****** Object:  Table [dbo].[CustomerSpeed]    Script Date: 11/04/2010 15:51:10 ******/
SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO

CREATE TABLE [dbo].[CustomerSpeed](
 [CustomerSpeedId] [int] NOT NULL,
 [CustomerId] [int] NULL,
 [SpeedId] [int] NOT NULL,
 [DiscountTypeId] [int] NOT NULL,
 [FlatFee] [money] NULL,
 [DiscountRate] [decimal](3, 3) NULL,
 CONSTRAINT [PK_AgentFee] PRIMARY KEY CLUSTERED 
(USE [PandaVisa2008]

GO

/****** Object:  Trigger [dbo].[TRG_CustomerSpeed_OnInsertUpdate]    Script Date: 11/04/2010 15:38:06 ******/
SET ANSI_NULLS ON

GO

SET QUOTED_IDENTIFIER ON

GO

ALTER TRIGGER [dbo].[TRG_CustomerSpeed_OnInsertUpdate]
ON [dbo].[CustomerSpeed]
FOR INSERT, UPDATE
AS
    BEGIN

        DECLARE @DiscountTypeId INT
        DECLARE @FlatFee MONEY
        DECLARE @DiscountRate DECIMAL(3, 3)

        SELECT
            @DiscountTypeId = DiscountTypeId,
            @FlatFee = FlatFee,
            @DiscountRate = DiscountRate
        FROM
            inserted

        IF @DiscountTypeId = 1
           AND @FlatFee IS NULL
            BEGIN
                RAISERROR (N'If @DiscountTypeId is 1, FlatFee must not be NULL',
                           10,
                           1)
            END

  IF @DiscountTypeId = 2
           AND @DiscountRate IS NULL
            BEGIN
                RAISERROR (N'If @DiscountTypeId is 2, @DiscountRate must not be NULL',
                           10,
                           1)
            END            
    END 

 [CustomerSpeedId] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY]

GO

ALTER TABLE [dbo].[CustomerSpeed]  WITH CHECK ADD  CONSTRAINT [CK_CustomerSpeed] CHECK  (([DiscountRate]>(0) AND [DiscountRate]<(1)))
GO

ALTER TABLE [dbo].[CustomerSpeed] CHECK CONSTRAINT [CK_CustomerSpeed]
GO

修改的

我得到了它的工作。我没有读过触发器来弥补我基本上缺乏理解，但他似乎工作，虽然我相信Check Constraint是更好的方法：

ALTER TRIGGER [dbo].[TRG_CustomerSpeed_OnInsertUpdate]
ON [dbo].[CustomerSpeed]
FOR INSERT, UPDATE
AS
    BEGIN
        IF EXISTS (SELECT
                       1
                   FROM
                       inserted I
                   WHERE  I.DiscountTypeId = 1
                      AND I.FlatFee IS NULL)
            BEGIN
                ROLLBACK TRANSACTION

                RAISERROR (N'If DiscountTypeId is 1, FlatFee must not be NULL',
                           10,
                           1)
            END

       IF EXISTS (SELECT
                       1
                   FROM
                       inserted I
                   WHERE  I.DiscountTypeId = 2
                      AND I.DiscountRate IS NULL)
            BEGIN
                ROLLBACK TRANSACTION

                RAISERROR (N'If DiscountTypeId is 2, DiscountRate must not be NULL',
                           10,
                           1)
            END            
    /*
     IF @DiscountTypeId = 2
        AND @DiscountRate IS NULL
         BEGIN
         Rollback Transaction
             RAISERROR (N'If @DiscountTypeId is 2, DiscountRate must not be NULL',
                        10,
                        1)
         END
    */
    END 

Your comments are welcomed.

Answer 1

我使用CHECK约束，而不是触发器

ALTER TABLE Mytable WITH CHECK ADD
   CONSTRAINT CK_MyTable_GoodName CHECK (
        NOT (DiscountTypeId = 1 AND Flatfee IS NULL)
        AND
        NOT (DiscountTypeId = 2 AND DiscountRate IS NULL)
)

另外，需要考虑“如果DiscountTypeId＆lt;＆gt; 1，Flatfee必须为NULL”等等

Answer 2

你从根本上不理解触发器。您需要做的第一件事是阅读有关联机丛书中的触发器，特别强调了解插入和删除的psuedotables。接下来你需要知道的是触发器应该永远不会被写入，就好像它一次只能处理一条记录一样。触发器对批量记录进行操作，触发器代码必须考虑到这一点。

Answer 3

我不相信触发器会引发错误，问题＃1。

轻松触发问题

修改的

3 个答案:

轻松触发问题

修改 的

3 个答案:

修改的