在数据库网格中显示MySql TIMEDIFF() [英] Displaying a MySql TIMEDIFF() in a DB grid

问题描述

当我使用命令行时，此查询给我令人愉悦的结果(它显示持续时间，这就是TIMEDIFF的含义):

When I use the command line, this query gives me pleasing results (it shows duation, which is what TIMEDIFF is about):

mysql> select timediff(end_time_stamp,start_time_stamp) from test_runs;
+-------------------------------------------+
| timediff(end_time_stamp,start_time_stamp) |
+-------------------------------------------+
| 00:00:07                                  |
| 00:00:11                                  |
| 00:01:23                                  |
+-------------------------------------------+
3 rows in set (0.00 sec)

当我将其放入Delphi的数据库网格中时，TIMEDIFF的格式类似于 12:00:07 AM ，这不是我想要的(看起来像一个时间，而不是一个持续时间)

When I put it in a DB grid in Delp the TIMEDIFFs are formatted like 12:00:07 AM, which is not what I want (that looks like a time, not a duration).

我正在使用AnyDac，当我在设计时打开查询编辑器并执行它时，结果也是 12:00:07 AM ，所以看来AnyDac正在出于某种原因对其进行格式化

I am using AnyDac and when I open the query editor at design time and execute it, the result is also 12:00:07 AM, so it seems that AnyDac is formatting it for some reason.

如何获得00:00:07这样的输出(持续时间而不是时间)?

How can I get output like 00:00:07 (a duration, not a time)?

• 我可以调整AnyDac查询吗?
• 我可以使用MySql语句显式格式化输出吗?
• 是否有一个OnXXX()函数，可以对其进行重新编码(以及如何编码)?

[更新]好吧，这段丑陋的代码符合我的要求，但是还有更优雅的方法吗?

[Update] Well, this ugly piece of code does what I want, but is there a more elegant way?

SELECT run_id,
       start_time_stamp,
       end_time_stamp,
       CONCAT(CONCAT(CONCAT(CONCAT(LPAD(EXTRACT(HOUR FROM timediff(end_time_stamp,start_time_stamp)), 2, '0'), ":"),LPAD(EXTRACT(MINUTE FROM timediff(end_time_stamp,start_time_stamp)), 2, '0'), ":"), LPAD(EXTRACT(SECOND FROM timediff(end_time_stamp,start_time_stamp)), 2, '0'))) AS duration,
       description

FROM test_runs ORDER BY start_time_stamp DESC

推荐答案

使用 TField 对象的"nofollow"> DisplayFormat 属性以获取所需的结果，例如:

Use the DisplayFormat property of the TField object to get the result you want, for example:

begin
  MyQuery.Open;
  MyQueryField.DisplayFormat := 'hh:nn:ss';
  //or casting a TField to a descendant, like this:
  (MyQuery.FieldByName('duration') as TDateTimeField).DisplayFormat := 'hh:nn:ss';
end;

编辑

我向TDateTimeField添加了强制类型转换.如果您的实际字段不是TDateTimeField的实例或后代，则将导致EInvalidTypeCast异常，因为您必须将其强制转换为它所属的正确类.

Edit

I added a cast to TDateTimeField. If your actual field is not an instance of TDateTimeField or a descendant it will result in a EInvalidTypeCast exception, since you have to cast it to the correct class it belongs to.

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