MySQL group by对单字分组序和多字段分组的方法讲解

我这里创建了一个 Goods 表，先看下里面的数据：

Mysql> select * from goods;
+----+------+------+------------+-------------+------------+
| id | s_id | b_id | goods_name | goods_price | goods_desc |
+----+------+------+------------+-------------+------------+
| 1 |  1 |  5 | book    |    22.35 | book    |
| 2 |  2 |  5 | ball    |    32.25 | ball    |
| 3 |  3 |  5 | NULL    |    3.23 | NULL    |
| 4 |  3 |  5 | Macbook  |    3.23 | book    |
| 5 |  3 |  5 | listbook  |    2.30 | book    |
| 6 |  1 |  1 | nicebook  |   9999.00 | nicebook  |
| 7 |  2 |  3 | googlebook |    25.30 | book    |
+----+------+------+------------+-------------+------------+