触发器在数据不存在时将其识别为重复数据

我在SQL Server中有一个触发器:

CREATE TRIGGER MyTrigger ON [dbo].[practiseduplicates]   
AFTER INSERT
AS
    IF EXISTS (SELECT * 
               FROM [practiseduplicates] t 
               INNER JOIN inserted i ON i.[money] = t.[money] 
                                     AND i.[Name] = t.[Name] 
                                     AND i.[year month] = t.[year month])
    BEGIN
        ROLLBACK
        RAISERROR ('Duplicated Data', 16, 1);
    END

然后插入这些值(已在数据表中):

insert into [practiseduplicates]
values ('2017-02', 'buzzlightyear', '10.09')

例如

'2056-12', 'mr potato head', '12345.09'

错误消息仍然会弹出,实际上它应该刚刚将数据插入表中,有人知道为什么会这样吗?