php - 行之间的时间差

Question

我必须遵循下面的查询图1，它有效，但我想做的是获取第4行和第5行之间的时间差，然后获取第5行和第6行之间的差异.

目标是得到类似图2的东西。理想情况下，我想在查询中执行此操作，而不必循环遍历数据库中的每一行，然后返回 PHP。

提前致谢。

<小时/>

图1

select * from ModuleFlowModuleStatus where ModuleCode = "LW2205" ORDER BY UpdatedOn;


| ID  | Module | MoudleStatus            | UpdatedOn           |

|   4 | LW2205 | Draft exam received     | 2017-10-18 12:41:12 |

|   5 | LW2205 | Draft exam received     | 2017-10-18 12:41:23 |

|   7 | LW2205 | Draft exam received     | 2017-10-20 15:06:46 |

| 275 | LW2205 | Exam approved by Dean   | 2017-11-14 16:39:28 |

| 288 | LW2205 | Final exam sign off by  | 2017-11-21 12:28:59 |

| 295 | LW2205 | Exam sent to SREO (Stud | 2017-11-23 09:53:30 |

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

<小时/>

图 2 预期结果

| ID  | Module | MoudleStatus            | UpdatedOn           | Diff(days)

|   4 | LW2205 | Draft exam received     | 2017-10-18 12:41:12 | 0

|   5 | LW2205 | Draft exam received     | 2017-10-18 12:41:23 | 0

|   7 | LW2205 | Draft exam received     | 2017-10-20 15:06:46 | 2

| 275 | LW2205 | Exam approved by Dean   | 2017-11-14 16:39:28 | 24

| 288 | LW2205 | Final exam sign off by  | 2017-11-21 12:28:59 | 7

| 295 | LW2205 | Exam sent to SREO (Stud | 2017-11-23 09:53:30 | 3

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

Answer 1

此 SQL 代码应该适用于应用于图 1 中的表:

SELECT
  t1.ID,
  t1.Module,
  t1.MoudleStatus,
  t1.UpdatedOn,
  IFNULL(DATEDIFF(
    t1.UpdatedOn,
    (SELECT MAX(t2.UpdatedOn) FROM ModuleFlowModuleStatus AS t2 WHERE t2.id < t1.id)
  ), 0) AS `Diff(Days)`
FROM
  ModuleFlowModuleStatus AS t1;

代码可以稍微优化/改进，但它对我有用。我省略了 WHERE 和 ORDER BY 子句以简化我的代码，您只需再次添加它们即可。如果有帮助请告诉我。哦，MySQL DATEDIFF 函数默认返回以天为单位的值，我认为这正是您想要的。