函数语法：

group_concat( [DISTINCT]  要连接的字段   [Order BY 排序字段 ASC/DESC]   [Separator '分隔符'] )

下面举例说明：

select * from goods;  

+------+------+

| id| price|

+------+------+

|1 | 10|

|1 | 20|

|1 | 20|

|2 | 20|

|3 | 200 |

|3 | 500 |

+------+------+

6 rows in set (0.00 sec)

以id分组，把price字段的值在同一行打印出来，逗号分隔(默认)

select id, group_concat(price) from goods group by id;  

+------+--------------------+

| id| group_concat(price) |

+------+--------------------+

|1 | 10,20,20|

|2 | 20 |

|3 | 200,500|

+------+--------------------+

3 rows in set (0.00 sec)

以id分组，把price字段的值在一行打印出来，分号分隔 

select id,group_concat(price separator ';') from goods group by id;

+------+----------------------------------+

| id| group_concat(price separator ';') |

+------+----------------------------------+

|1 | 10;20;20 |

|2 | 20|

|3 | 200;500 |

+------+----------------------------------+

3 rows in set (0.00 sec)

以id分组，把去除重复冗余的price字段的值打印在一行，逗号分隔

select id,group_concat(distinct price) from goods group by id;  

+------+-----------------------------+

| id| group_concat(distinct price) |

+------+-----------------------------+

|1 | 10,20|

|2 | 20 |

|3 | 200,500 |

+------+-----------------------------+

3 rows in set (0.00 sec)

以id分组，把price字段的值打印在一行，逗号分隔，按照price倒序排列

select id,group_concat(price order by price desc) from goods group by id;  

+------+---------------------------------------+

| id| group_concat(price order by price desc) |

+------+---------------------------------------+

|1 | 20,20,10 |

|2 | 20|

|3 | 500,200|

+------+---------------------------------------+

3 rows in set (0.00 sec)