Question

我正在创建一个R sweave文件，该文件将编译一个软件测试数据的pdf报告。数据主要来自SQL服务器表，如下所示：

Comment.where(type: 'MagazineComment').all

我使用TestNum列可以更容易地逐步计算版本，因为它们是字符串。所以在我的R脚本中，我有一个应该找到最新版本的部分和之前的部分。

| FileName | Version | Category | Value |         Date        | TestNum |
|:--------:|:-------:|:--------:|:-----:|:-------------------:|:-------:|
| File1    | 1.0.12  | Run Time | 74    | 2016-10-01 12:00:00 | 1       |
| File1    | 1.0.12  | Totals   | 468   | 2016-10-01 12:00:00 | 1       |
| File1    | 1.0.12  | DB Size  | 589   | 2016-10-01 12:00:00 | 1       |
| File2    | 1.0.12  | Run Time | 81    | 2016-10-01 12:00:00 | 1       |
| File2    | 1.0.12  | Totals   | 351   | 2016-10-01 12:00:00 | 1       |
| File2    | 1.0.12  | DB Size  | 625   | 2016-10-01 12:00:00 | 1       |
| File1    | 1.0.15  | Run Time | 74    | 2016-10-01 12:00:00 | 2       |
| File1    | 1.0.15  | Totals   | 468   | 2016-10-01 12:00:00 | 2       |
| File1    | 1.0.15  | DB Size  | 589   | 2016-10-01 12:00:00 | 2       |
| File2    | 1.0.15  | Run Time | 81    | 2016-10-01 12:00:00 | 2       |
| File2    | 1.0.15  | Totals   | 351   | 2016-10-01 12:00:00 | 2       |
| File2    | 1.0.15  | DB Size  | 625   | 2016-10-01 12:00:00 | 2       |
| File1    | 1.0.17  | Run Time | 74    | 2016-10-01 12:00:00 | 3       |
| File1    | 1.0.17  | Totals   | 468   | 2016-10-01 12:00:00 | 3       |
| File1    | 1.0.17  | DB Size  | 589   | 2016-10-01 12:00:00 | 3       |
| File2    | 1.0.17  | Run Time | 81    | 2016-10-01 12:00:00 | 3       |
| File2    | 1.0.17  | Totals   | 351   | 2016-10-01 12:00:00 | 3       |
| File2    | 1.0.17  | DB Size  | 625   | 2016-10-01 12:00:00 | 3       |
| File1    | 1.0.21  | Run Time | 74    | 2016-10-01 12:00:00 | 4       |
| File1    | 1.0.21  | Totals   | 468   | 2016-10-01 12:00:00 | 4       |
| File1    | 1.0.21  | DB Size  | 589   | 2016-10-01 12:00:00 | 4       |
| File2    | 1.0.21  | Run Time | 81    | 2016-10-01 12:00:00 | 4       |
| File2    | 1.0.21  | Totals   | 351   | 2016-10-01 12:00:00 | 4       |
| File2    | 1.0.21  | DB Size  | 625   | 2016-10-01 12:00:00 | 4       |

然而，有时候一个版本的软件非常错误并且每次测试都会崩溃。这在图表中看起来非常有用，所以我只是在SQL数据库中添加一行我用来过滤掉它，然后R数据帧最终看起来像这样：

vLatest <- unique(df[df[,"TestNum"] == max(df$TestNum), "Version"])
vPrevious <- unique(df[df[,"TestNum"] == max(df$TestNum)-1, "Version"])

但是| FileName | Version | Category | Value | Date | TestNum | |:--------:|:-------:|:--------:|:-----:|:-------------------:|:-------:| | File1 | 1.0.12 | Run Time | 74 | 2016-10-01 12:00:00 | 1 | | File1 | 1.0.12 | Totals | 468 | 2016-10-01 12:00:00 | 1 | | File1 | 1.0.12 | DB Size | 589 | 2016-10-01 12:00:00 | 1 | | File2 | 1.0.12 | Run Time | 81 | 2016-10-01 12:00:00 | 1 | | File2 | 1.0.12 | Totals | 351 | 2016-10-01 12:00:00 | 1 | | File2 | 1.0.12 | DB Size | 625 | 2016-10-01 12:00:00 | 1 | | File1 | 1.0.15 | Run Time | 74 | 2016-10-01 12:00:00 | 2 | | File1 | 1.0.15 | Totals | 468 | 2016-10-01 12:00:00 | 2 | | File1 | 1.0.15 | DB Size | 589 | 2016-10-01 12:00:00 | 2 | | File2 | 1.0.15 | Run Time | 81 | 2016-10-01 12:00:00 | 2 | | File2 | 1.0.15 | Totals | 351 | 2016-10-01 12:00:00 | 2 | | File2 | 1.0.15 | DB Size | 625 | 2016-10-01 12:00:00 | 2 | | File1 | 1.0.21 | Run Time | 74 | 2016-10-01 12:00:00 | 4 | | File1 | 1.0.21 | Totals | 468 | 2016-10-01 12:00:00 | 4 | | File1 | 1.0.21 | DB Size | 589 | 2016-10-01 12:00:00 | 4 | | File2 | 1.0.21 | Run Time | 81 | 2016-10-01 12:00:00 | 4 | | File2 | 1.0.21 | Totals | 351 | 2016-10-01 12:00:00 | 4 | | File2 | 1.0.21 | DB Size | 625 | 2016-10-01 12:00:00 | 4 |仍在寻找vPrevious，因此脚本会中断。有没有办法可以查找第二个最高值呢？

编辑：根据建议，这是我用来创建数据框的查询内容。

TestNum == 3

Answer 1

您可以尝试将dense_rank与order by TestNum

一起使用

下面的代码段给出了它的用法示例。

select c.*
from (
    select *,dense_rank() over (order by [object_id] desc) as [row_number]
    from sys.columns
    ) c
where c.[row_number] in (1,2)

如果您可以将Sql查询添加到问题中，那么它可能有助于提供更有针对性的响应。

修改

为op的原始查询量身定制;

select FileName, Version, Category, Value, Date, TestNum from ( select FileName, Version, Category, Value, Date, TestNum , dense_rank() over (order by [TestNum] desc) as [row_number] from Table where Comments != 'Do Not Include in R Chart' ) t where t.[row_number] in (1,2)

找到第二个最高值而不是最大值＆＃34; -1＆＃34;

1 个答案: