将SQL Server触发器转换为MySQL

这是原始SQL Server 2008触发器：

    CREATE TRIGGER InsertVehTrig ON dbo.Vehicle   
    FOR INSERT AS   
        declare @Cph char(50),   
                @DevID char(12),   
                @VehID bigint,   
                @TmpID bigint,   
                @DevCount int  
    begin    
       set nocount on    

       select  @Cph = rtrim(ltrim(i.cph)), @VehID = i.ID, @DevID = DevID  
       from inserted i      

       if(@VehID is null)    
           return select @DevCount= count(id) from vehicle where (cph=@cph) or (DevID=@DevID) 
    --选择记录－－条件：当前的车牌号　或　设备ID   

       if ( @DevCount>1)  
    --如果记录数，超过1，则认为有重复    
          rollback tran      
       else if (@DevCount = 1)
       begin    
          select @TmpID = id from vehicle where (cph = @cph) or (DevID = @DevID)    

          if (@TmpID != @VehID) 
              --如果增加的车牌号码与数据库中的在相同的，则不允许增加     
              rollback tran    
       end      
       --增加，此时需要在Tbl_Toll中增加    

       /* insert into tbl_Toll (VehID,[Money], Payer, PayerTel, TollDate, ValidDate, Demo, UserName)
          values(@VehID, 0, 'LiaoYuan', '0755-26506932',   DATEADD(month, 1, getDate()), DATEADD(month, 13, getDate()), '' , 'admin' )*/          
       update vehicle set cph = @Cph where ID = @VehID  
   end          

我正在尝试将其转换为MySQl触发器

DROP TRIGGER IF EXISTS InsertVehTrig;

DELIMITER $$

CREATE TRIGGER InsertVehTrig AFTER INSERT
ON Vehicle FOR EACH ROW
   SWL_return:
BEGIN
   DECLARE Cph CHAR(50);
   DECLARE DevID CHAR(12);
   DECLARE VehID BIGINT;
   DECLARE TmpID BIGINT;
   DECLARE DevCount INT;

   SET Cph = rtrim(ltrim(NEW.cph));
   SET VehID = NEW.ID;
   SET DevID = NEW.DevID;

   if(VehID is null) then 
    select count(id) into @DevCount from vehicle where (cph=@Cph) or (DevID=@DevID);
-- 条件：当前的车牌号　或　设备ID
    end if;

   if (DevCount > 1) then  -- 如果记录数，超过1，则认为有重复   
      -- Rollback not supported in trigger
        SET @SWV_Null_Var = 0;
        Leave SWL_return;
   else 
      if (DevCount = 1) then
         select ID INTO @TmpID from Vehicle where (Vehicle.cph = @Cph) or (Vehicle.DevID = @DevID);
         if (TmpID != VehID) then -- --如果增加的车牌号码与数据库中的在相同的，则不允许增加
            -- Rollback not supported in trigger
                Leave SWL_return;
                SET @SWV_Null_Var = 0;
         end if;
      end if;
   end if;

   update vehicle set cph = @Cph where ID = @VehID;
END;

问题

在变量之前使用

@

正确吗？据我所知，SQL Server使用

@

作为变量声明。但我不知道MySQL是否有效

SQL Server有

rollback tran

对于MySQL，我应该将其更改为什么？当我想取消插入数据操作时，如何替换MySQL中的as

rollback

什么是

SET@SWV\u Null\u Var=0意义？我没有看到这个变量的任何声明？这是什么

---

完成从MS SQL到MY SQL的转换 /* 防止用户插入的数据中，车牌号码的前后含有空格，此处是将这样的空格去掉 程宪平－－－－－2009－04－19
修改记录： 2009－04－23
修改原因：　车牌必须唯一，德维德也必须唯一，所以其一致性必须通过数据库自身来进行处理，保证一致性 */ 如果存在插入式触发器，则触发

DELIMITER $$

CREATE TRIGGER InsertVehTrig after INSERT
ON Vehicle FOR EACH ROW
   SWL_return:
BEGIN
   DECLARE TmpID BIGINT;
   DECLARE DevCount INT;
   DECLARE msg VARCHAR(255);

    DECLARE New_Cph VARCHAR(100);
    SET New_Cph = NEW.Cph;

select count(id) into DevCount from vehicle where (vehicle.Cph=New_Cph) or (vehicle.DevID=New.DevID);

   if (DevCount > 1) then  -- 如果记录数，超过1，则认为有重复   
        set msg = concat('Cannot Create Same CPH or DevID : \r\nDevCount=',DevCount,'\r\nCPH=',New_Cph,'\r\nDevID=',New.DevID);
        SIGNAL sqlstate '45001' set message_text = msg;
   else 
      if (DevCount = 1) then
         select ID INTO TmpID from Vehicle where (Vehicle.Cph = New_Cph) or (Vehicle.DevID = New.DevID);
         if (TmpID != New.ID) then -- --如果增加的车牌号码与数据库中的在相同的，则不允许增加
            set msg = concat('Cannot Create Same CPH or DevID : \r\nTmpID=',TmpID,'\r\nCPH=',New_Cph,'\r\nDevID=',New.DevID);
            SIGNAL sqlstate '45001' set message_text = msg;
         end if;
      end if;
   end if;

END;

在MySql中，这用于取消Insert语句

set msg = concat('Cannot Create Same CPH or DevID : \r\nTmpID=',TmpID,'\r\nCPH=',New_Cph,'\r\nDevID=',New.DevID);
SIGNAL sqlstate '45001' set message_text = msg;

---

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