现在有两张表

mysql> select * from goods;
+----+------+---------+
| id | name | price   |
+----+------+---------+
|  1 | 苹果 |    3.25 |
|  2 | 香蕉 |    2.50 |
|  3 | 电脑 | 1200.00 |
|  4 | 电脑 | 1200.00 |
|  5 | 耳机 |   55.00 |
|  6 | 手机 |  600.00 |
+----+------+---------+

mysql> SELECT * FROM `test`.`order`;
+----+--------+----------+
| id | number | goods_id |
+----+--------+----------+
|  1 |      1 |        3 |
|  2 |      2 |        1 |
|  3 |      3 |        4 |
|  4 |      4 |        3 |
|  5 |      5 |        2 |
|  6 |      6 |        5 |
|  7 |      7 |        6 |
|  8 |      8 |        2 |
|  9 |      9 |        1 |
| 10 |     10 |        3 |
| 11 |     11 |        5 |
| 12 |     12 |        6 |
| 13 |     13 |        2 |
| 14 |     14 |        5 |
| 15 |     15 |        1 |
+----+--------+----------+

统计哪件商品销售最多

SELECT
    `order`.goods_id,
    COUNT( `order`.goods_id ) AS num
FROM
    `order`
GROUP BY
    `order`.goods_id
ORDER BY
    num DESC

统计哪件商品销售最多 + 商品名字

SELECT
    `order`.goods_id,
    COUNT( `order`.goods_id ) AS num,
    goods.`name`
FROM
    `order`
    INNER JOIN goods ON `order`.goods_id = goods.id
GROUP BY
    `order`.goods_id
ORDER BY
    num DESC