mysql> select * from table1;

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

| name_new | transactor | pid | order_date          |

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

| 1hahha   | 1xiaohong  |    | -- :: |

| 2hahha   | 2xiaohong  |    | -- :: |

| 3hahha   | 3xiaohong  |    | -- :: |

| 4hahha   | 4xiaohong  |    | -- :: |

| 3hahha   | bob        |    | -- :: |

| 3hahha   | lee        |    | -- :: |

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

 rows in set (0.00 sec)

mysql> select avg(pid) from table1;

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

| avg(pid) |

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

|   3.5000 |

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

 row in set (0.00 sec)

mysql> select (/);

+--------+

| (/) |

+--------+

| 3.5000 |

+--------+

 row in set (0.00 sec)