易飞ERP触发器保存时空白字段提示不可空白

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
ALTER TRIGGER [dbo].[tr_INSERTCOPTD] ON [dbo].[COPTD] 
FOR INSERT
AS
 DECLARE @TD001 CHAR(4),--单别
         @TD002 CHAR(11),--单号
         @TD003 CHAR(4),--序号
         @TD021 CHAR(1),
         @TD011 NUMERIC(15,6),
          @UDF01 VARCHAR(255)--单价

BEGIN TRANSACTION
 SET NOCOUNT ON
 SELECT @TD001=TD001,@TD002=TD002,@TD003=TD003,@TD021=TD021,@UDF01=UDF01,@TD011=TD011 FROM INSERTED
 IF @UDF01=''
 BEGIN
 RAISERROR('%样品编号为空不允许下',16,1,@TD003)
 END
 SET NOCOUNT OFF
COMMIT TRANSACTION