MySQL group by 单字分组序和多字段分组

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       |
+----+------+------+------------+-------------+------------+

1、根据s_id分组

mysql> select *,group_concat(goods_name) goods_names,group_concat(goods_desc) goods_descs,group_concat(id) ids,group_concat(goods_price) goods_prices  from goods group by s_id;
+----+------+------+------------+-------------+------------+------------------+---------------+-------+----------------+
| id | s_id | b_id | goods_name | goods_price | goods_desc | goods_names      | goods_descs   | ids   | goods_prices   |
+----+------+------+------------+-------------+------------+------------------+---------------+-------+----------------+
|  1 |    1 |    5 | book       |       22.35 | book       | book,nicebook    | book,nicebook | 1,6   | 22.35,9999.00  |
|  2 |    2 |    5 | ball       |       32.25 | ball       | ball,googlebook  | ball,book     | 2,7   | 32.25,25.30    |
|  3 |    3 |    5 | NULL       |        3.23 | NULL       | macbook,listbook | book,book     | 3,4,5 | 3.23,3.23,2.30 |
+----+------+------+------------+-------------+------------+------------------+---------------+-------+----------------+

这里使用了 group_concat() 函数，主要目的是为了显示分组的详细信息

上面的根据单个字段分组很简单，把相同s_id的记录都归组了

2、根据s_id,goods_desc字段分组

分析：这里查询分组时，会先根据s_id分组，然后对每个组里面的数据再根据goods_desc进行分组

mysql> select *,group_concat(goods_name) goods_names,group_concat(goods_desc) goods_descs,group_concat(id) ids,group_concat(goods_price) goods_prices  from goods group by s_id,goods_desc;
+----+------+------+------------+-------------+------------+------------------+-------------+------+--------------+
| id | s_id | b_id | goods_name | goods_price | goods_desc | goods_names      | goods_descs | ids  | goods_prices |
+----+------+------+------------+-------------+------------+------------------+-------------+------+--------------+
|  1 |    1 |    5 | book       |       22.35 | book       | book             | book        | 1    | 22.35        |
|  6 |    1 |    1 | nicebook   |     9999.00 | nicebook   | nicebook         | nicebook    | 6    | 9999.00      |
|  2 |    2 |    5 | ball       |       32.25 | ball       | ball             | ball        | 2    | 32.25        |
|  7 |    2 |    3 | googlebook |       25.30 | book       | googlebook       | book        | 7    | 25.30        |
|  3 |    3 |    5 | NULL       |        3.23 | NULL       | NULL             | NULL        | 3    | 3.23         |
|  4 |    3 |    5 | macbook    |        3.23 | book       | macbook,listbook | book,book   | 4,5  | 3.23,2.30    |
+----+------+------+------------+-------------+------------+------------------+-------------+------+--------------+

这里的goods_descs 和 上面的一比较就明白了

接下来还可以再根据 goods_price 分组

mysql> select *,group_concat(goods_name) goods_names,group_concat(goods_desc) goods_descs,group_concat(id) ids,group_concat(goods_price) goods_prices  from goods group by s_id,goods_desc,goods_price;
+----+------+------+------------+-------------+------------+-------------+-------------+------+--------------+
| id | s_id | b_id | goods_name | goods_price | goods_desc | goods_names | goods_descs | ids  | goods_prices |
+----+------+------+------------+-------------+------------+-------------+-------------+------+--------------+
|  1 |    1 |    5 | book       |       22.35 | book       | book        | book        | 1    | 22.35        |
|  6 |    1 |    1 | nicebook   |     9999.00 | nicebook   | nicebook    | nicebook    | 6    | 9999.00      |
|  2 |    2 |    5 | ball       |       32.25 | ball       | ball        | ball        | 2    | 32.25        |
|  7 |    2 |    3 | googlebook |       25.30 | book       | googlebook  | book        | 7    | 25.30        |
|  3 |    3 |    5 | NULL       |        3.23 | NULL       | NULL        | NULL        | 3    | 3.23         |
|  5 |    3 |    5 | listbook   |        2.30 | book       | listbook    | book        | 5    | 2.30         |
|  4 |    3 |    5 | macbook    |        3.23 | book       | macbook     | book        | 4    | 3.23         |
+----+------+------+------------+-------------+------------+-------------+-------------+------+--------------+

总结：这里主要是进行多个字段分组的时候，只需掌握分组顺序后面的字段是根据前面字段分组后的内容再进行的分组即可。