(select t1.goods_id goods_id from 1dcq_goods t1 order by t1.goods_id ) UNION all (select t2.goods_id goods_id from 1dcq_goods t2 order by t2.goods_id desc ) 如上sql语句，结果如下，可以看出是没有顺序的： 下面语句： (select t1.goods_id goods_id from 1dcq_goods t1 order by t1.goods_id limit 999999999 ) UNION all (select t2.goods_id goods_id from 1dcq_goods t2 order by t2.goods_id desc limit 999999999) 结果如下，可以看出是排序的，一个升序，一个降序，然后合并： 可见"limit"关键字不能少！
