我有以下数据表和数据：

mysql> describe school_data_sets_numeric_data;

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

| Field | Type | Null | Key | Default | Extra |

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

| id | int(11) | NO | PRI | NULL | auto_increment |

| data_set_nid | int(11) | NO | | NULL | |

| school_nid | int(11) | NO | | NULL | |

| year | int(11) | NO | | NULL | |

| description | varchar(255) | NO | | NULL | |

| value | decimal(18,12) | NO | | NULL | |

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

6 rows in set (0.00 sec)

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

| id | data_set_nid | school_nid | year | description | value |

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

| 54 | 19951 | 19944 | 2008 | Asian | 75.000000000000 |

| 51 | 19951 | 19944 | 2008 | White | 200.000000000000 |

| 52 | 19951 | 19944 | 2008 | African American | 100.000000000000 |

| 53 | 19951 | 19944 | 2008 | Hispanic | 50.000000000000 |

| 55 | 19951 | 19944 | 2008 | Native American | 9.000000000000 |

我想显示数据的平均值而不是原始数字.我想在原始sql中执行此操作.

例：

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

| id | data_set_nid | school_nid | year | description | average |

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

| 54 | 19951 | 19944 | 2008 | Asian | 17.28% |

| 51 | 19951 | 19944 | 2008 | White | 46.06% |

| 52 | 19951 | 19944 | 2008 | African American | 23.04% |

| 53 | 19951 | 19944 | 2008 | Hispanic | 11.52% |

| 55 | 19951 | 19944 | 2008 | Native American | 2.07% |

做这个的最好方式是什么？请记住,将有多个数据集和年份.