mysql sum()函数 , 计算总和

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 * from table1 where minute(order_date)=;
+----------+------------+-----+---------------------+
| name_new | transactor | pid | order_date          |
+----------+------------+-----+---------------------+
| 3hahha   | 3xiaohong  |    | -- :: |
| 4hahha   | 4xiaohong  |    | -- :: |
| 3hahha   | bob        |    | -- :: |
| 3hahha   | lee        |    | -- :: |
+----------+------------+-----+---------------------+
 rows in set (0.00 sec)

mysql> select sum(pid) as pidsum from table1 where minute(order_date)=;
+--------+
| pidsum |
+--------+
|      |
+--------+
 row in set (0.00 sec)