Question

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）Windows NT 6.1上的Microsoft Corporation标准版（64位）（Build 7601：Service Pack 1））（管理程序）。我是sql server和procedures / triggers的新手。我有以下代码来创建一个触发器（它工作）：

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

如果触发器尚不存在，我如何有条件地创建？我在这做错了什么？ Stackoverflow有很好的例子＆＃34;如果不存在＆＃34;，但我不能让它与CREATE一起工作。这是我失败的努力之一：

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

Answer 1

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：

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


 '

Answer 2

最好的方法是检查对象，如果它们存在则删除它们，然后再创建它们。

相反，如果它存在则根本不创建它，我会以另一种方式接近它，如果存在则删除它然后创建。

通常在长度较长的脚本中，如果要更新触发器的定义，只需在该脚本的末尾添加它，您的触发器定义就会更新。

因此，方法应为create the object but drop it if it already exists，而不是dont create it at all if it already exists

IF OBJECT_ID ('[Insert_WithdrawalCodes] ', 'TR') IS NOT NULL
   DROP TRIGGER [Insert_WithdrawalCodes];
GO

CREATE TRIGGER .......

Answer 3

某些语句（如CREATE TRIGGER）需要成为批处理中的第一个语句（例如，由GO分隔的语句组）。

https://msdn.microsoft.com/en-us/library/ms175502.aspx

或者你可以这样做

IF NOT EXISTS ( SELECT  *
            FROM    sys.objects
            WHERE   type = 'TR'
                    AND name = 'Insert_WithdrawalCodes' ) 
BEGIN
    EXEC ('CREATE TRIGGER Insert_WithdrawalCodes ON ...');
END;

Answer 4

正如上面的其他答案中没有提到的重点，我写了这个答案：

当我们想在sys.objects表中查找触发器或其他对象时，最好在where子句中准确地检查（使用架构或object_id等），以避免同名无效结果。考虑一下另一个模式中何时已经存在另一个具有相同名称的触发器... 因此，由于sys.object表包含一个schema_id列，因此我们可以使用name和type列之外的其他列来更准确地进行查询，如下面的示例所示。 / p>
正如Microsoft文档在“触发器限制”下提到的here：

CREATE TRIGGER必须是批处理中的第一条语句，并且可以应用只能放在一张桌子上。

因此，我们使用EXECUTE来克服此限制：

IF NOT EXISTS (select * from sys.objects where schema_id=SCHEMA_ID('dbo') AND type='TR' and name='Insert_WithdrawalCodes')
BEGIN
   EXECUTE ('CREATE TRIGGER [Insert_WithdrawalCodes] ON [dbo].[PupilWithdrawalReason]
   AFTER INSERT
   AS 
   BEGIN
      SET NOCOUNT ON;
      ...
   END');
END

Answer 5

检查IF是否存在触发

IF EXISTS (SELECT * FROM sys.objects WHERE [name] = 
                 N'[Trigger_Name]' AND [type] = 'TR')
 BEGIN
 DROP TRIGGER [Trigger_Name]
 Print('Trigger dropped => [Schema].[Trigger_Name]')
 END
 GO

检查存在过程的IF存在，功能也可以通过单击下面的链接 http://www.gurujipoint.com/2017/05/check-if-exist-for-trigger-function-and.html

如何添加＆＃34; IF NOT NOT EXISTS＆＃34;创建触发器语句

5 个答案: