直接上例子了，查询近一周TOP20的订单商品。
mysql> select (@ii:= @ii+1) as "序号", otmp.* from (select sku_id as "SKU_ID",count(*) as "数量" from order where order_time BETWEEN DATE_SUB(CURDATE(), INTERVAL 7 DAY) and CURDATE() group by 1 order by 2 desc limit 20) otmp,(SELECT @ii:=0) as ii
;
+------+--------------+----+
| 序号 | SKU_ID | 数量 |
+------+--------------+----+
| 1 | 100115 | 212 |
| 2 | 572205 | 139 |
| 3 | 533736 | 112 |
| 4 | 13206 | 88 |
| 5 | 5259 | 68 |
+------+--------------+----+