如何添加“如果不存在"创建触发语句 [英] How to add "IF NOT EXISTS" to create trigger statement

问题描述

我使用的是 sql server 2008 R2.更具体地说，Microsoft SQL Server 2008 R2 (RTM) - 10.50.1600.1 (X64) 2010 年 4 月 2 日 15:48:46 版权所有 (c) Microsoft Corporation 标准版(64 位)，Windows NT 6.1(内部版本 7601:Service Pack 1))(管理程序).我是 sql server 和程序/触发器的新手.我有以下代码来创建触发器(它有效):

I am using sql server 2008 R2. More specifically, Microsoft SQL Server 2008 R2 (RTM) - 10.50.1600.1 (X64) Apr 2 2010 15:48:46 Copyright (c) Microsoft Corporation Standard Edition (64-bit) on Windows NT 6.1 (Build 7601: Service Pack 1) (Hypervisor). I am new to sql server and procedures/triggers. I have the following code to create a trigger (it works):

CREATE TRIGGER [dbo].[Insert_WithdrawalCodes] 
   ON  [dbo].[PupilWithdrawalReason] 
   AFTER INSERT
AS 
BEGIN
    SET NOCOUNT ON;
        UPDATE [dbo].[PupilWithdrawalReason] SET DateCreated=dbo.SYSTEMTIME() 
        WHERE WithdrawalCodeID IN (SELECT WithdrawalCodeID FROM inserted)
END

如何仅在触发器尚不存在的情况下有条件地创建?我在这里做错了什么?StackOverflow 有很好的 IF NOT EXISTS 示例，但我无法将其与 CREATE 结合使用.这是我失败的尝试之一:

How do I conditionally create only if the trigger does not yet exist? What am I doing wrong here? StackOverflow has good examples of IF NOT EXISTS, but I can't get this to work in conjunction with a CREATE. Here is one of my failed efforts:

IF NOT EXISTS (SELECT * FROM sys.objects WHERE type = 'TR' AND name = 'Insert_WithdrawalCodes')
   exec('CREATE TRIGGER [dbo].[Insert_WithdrawalCodes] ON  [dbo].[PupilWithdrawalReason] AFTER INSERT AS BEGIN SET NOCOUNT ON; UPDATE [dbo].[PupilWithdrawalReason] SET DateCreated=dbo.SYSTEMTIME() WHERE WithdrawalCodeID IN (SELECT WithdrawalCodeID FROM inserted) END')
GO

推荐答案

IF EXISTS (SELECT * FROM sys.triggers WHERE object_id = OBJECT_ID(N'[dbo].[TRIGGERNAME]'))
DROP TRIGGER [dbo].[TRIGGERNAME]
go
IF  EXISTS (SELECT * FROM dbo.sysobjects WHERE id = OBJECT_ID(N'[dbo].[TABLENAME]') AND OBJECTPROPERTY(id, N'IsUserTable') = 1)
BEGIN
CREATE   TRIGGER [dbo].[TRIGGERNAME] ON [dbo].[TABLENAME] FOR INSERT, UPDATE 

AS ...

END

根据您更新的问题...试试这个:

Based on your updated question... try this:

IF NOT EXISTS (select * from sys.objects where type = 'TR' and name = 'Insert_WithdrawalCodes')
EXEC dbo.sp_executesql @statement = N'

CREATE TRIGGER [dbo].[Insert_WithdrawalCodes] 
   ON  [dbo].[PupilWithdrawalReason] 
   AFTER INSERT
AS 
BEGIN
    SET NOCOUNT ON;
        UPDATE [dbo].[PupilWithdrawalReason] SET DateCreated=dbo.SYSTEMTIME() 
        WHERE WithdrawalCodeID IN (SELECT WithdrawalCodeID FROM inserted)
END


 '

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