Question

我正在尝试将当前项目持续时间与项目名称存储在一个表中。它还包括当前持续时间，前一个持续时间和总持续时间。

我在表单中输入项目名称和当前持续时间并存储到表中，但是当我添加更多项目时，如何计算之前的持续时间和总持续时间？

projects_id - int (auto increment)
project - varchar
current_time - int
previous_time - int
total_time - int

首先，我会将previous_time和total_time初始化为0

然后在插入新行时，我将更新项目名称和当前时间，必须自动计算上一次和总时间。

Answer 1

您可以考虑的表格结构：

mysql> desc project;
+---------------+-------------+------+-----+---------------------+----------------------------+
| Field         | Type        | Null | Key | Default             | Extra                      |
+---------------+-------------+------+-----+---------------------+----------------------------+
| project_id    | int(1)      | NO   | PRI | NULL                | auto_increment             |
| project       | varchar(20) | YES  |     | NULL                |                            |
| current_t     | timestamp   | NO   |     | CURRENT_TIMESTAMP   | on update CURRENT_TIMESTAMP|
| previous_time | timestamp   | NO   |     | 0000-00-00 00:00:00 |                            |
| total_time    | time        | YES  |     | NULL                |                            |
+---------------+-------------+------+-----+---------------------+----------------------------+
5 rows in set (0.01 sec)

示例数据

mysql> select * from project;
+------------+---------+---------------------+---------------------+------------+
| project_id | project | current_t           | previous_time       | total_time |
+------------+---------+---------------------+---------------------+------------+
|          1 | test    | 2014-03-06 12:36:34 | 2014-03-06 10:27:19 | 00:00:00   |
+------------+---------+---------------------+---------------------+------------+
1 row in set (0.00 sec)

执行您要查找的更新的SQL：

REPLACE INTO project (project_id,previous_time,total_time) 
SELECT project_id,current_t,total_time + TIMEDIFF(NOW(),current_t) 
FROM project 
WHERE project_id = 1

更新的表格：

mysql> select * from project;
+------------+---------+---------------------+---------------------+------------+
| project_id | project | current_t           | previous_time       | total_time |
+------------+---------+---------------------+---------------------+------------+
|          1 | NULL    | 2014-03-06 12:41:22 | 2014-03-06 12:36:34 | 00:04:48   |
+------------+---------+---------------------+---------------------+------------+
1 row in set (0.00 sec)

插入当前时间时如何计算以前的时间和总时间？

1 个答案: