更具a表中的字段对b表中的列的增添删的触发器

a表：Fields

b表：Customeres

--添加数据时的触发器
set ANSI_NULLS ON
set QUOTED_IDENTIFIER ON
go

create TRIGGER [trigger_addField] ON [dbo].[Fields] 
 FOR INSERT 
 AS   
DECLARE @FieldID int,  
 @Name varchar(50),   
@DataType varchar(50),  
 @SQL varchar(1000)   
SELECT @FieldID = FieldID,
 @Name = [Name],
 @DataType = 'varchar(64)'
FROM Inserted  
if not exists (SELECT * FROM syscolumns    where id=object_id('Customeres') AND name=@Name)  
BEGIN   
SET @SQL = 'ALTER table Customeres add ' + @Name + ' '+ @DataType 
  EXEC (@SQL)  
END 
 PRINT 
@Name + ',' + @DataType 


--改变数据时的触发器
set ANSI_NULLS ON
set QUOTED_IDENTIFIER ON
go

alter trigger [tgr_updateField]
on [dbo].[Fields] 
    for update
as declare @oldName varchar(20), @newName varchar(20),@aa varchar(20),@SQL varchar(1000) ;
    --更新前的数据
    select @oldName = name from deleted;

 --更新后的数据
    select @newName = name from inserted;
    if not exists (SELECT * FROM syscolumns    where id=object_id('Customeres') AND name=@newName)  
    select @aa='Customeres.'+@oldName;
BEGIN 
EXEC   sp_rename  @aa, @newName,'COLUMN';
END 


--删除数据时的触发器
set ANSI_NULLS ON
set QUOTED_IDENTIFIER ON
go

create TRIGGER [trigger_deletField] ON [dbo].[Fields] 
 FOR delete 
 AS   
DECLARE  
 @Name varchar(50),   
 @SQL varchar(1000);
SELECT @Name = [Name] from deleted;
if  exists (SELECT * FROM syscolumns    where id=object_id('Customeres') AND name=@Name)  
BEGIN   
SET @SQL = 'alter table Customeres DROP COLUMN ' + @Name 
  EXEC (@SQL)  
END