ROW_NUMBER（）显示意外值 [英] ROW_NUMBER() shows unexpected values

问题描述

我的表的值类似（ RowCount 由下面的查询生成）：

My table has values like (RowCount is generated by the query below):

ID       Date_trans   Time_trans  Price  RowCount
-------  -----------  ----------  -----  --------
1699093  22-Feb-2011  09:30:00    58.07  1
1699094  22-Feb-2011  09:30:00    58.08  1
1699095  22-Feb-2011  09:30:00    58.08  2
1699096  22-Feb-2011  09:30:00    58.08  3
1699097  22-Feb-2011  09:30:00    58.13  1
1699098  22-Feb-2011  09:30:00    58.13  2
1699099  22-Feb-2011  09:30:00    58.12  1
1699100  22-Feb-2011  09:30:08    58.13  3
1699101  22-Feb-2011  09:30:09    57.96  1
1699102  22-Feb-2011  09:30:09    57.95  1
1699103  22-Feb-2011  09:30:09    57.93  1
1699104  22-Feb-2011  09:30:09    57.96  2
1699105  22-Feb-2011  09:30:09    57.93  2
1699106  22-Feb-2011  09:30:09    57.93  3
1699107  22-Feb-2011  09:30:37    58     1
1699108  22-Feb-2011  09:30:37    58.08  4
1699109  22-Feb-2011  09:30:38    58.08  5
1699110  22-Feb-2011  09:30:41    58.02  1
1699111  22-Feb-2011  09:30:41    58.02  2
1699112  22-Feb-2011  09:30:41    58.01  1
1699113  22-Feb-2011  09:30:41    58.01  2
1699114  22-Feb-2011  09:30:41    58.01  3
1699115  22-Feb-2011  09:30:42    58.02  3
1699116  22-Feb-2011  09:30:42    58.02  4
1699117  22-Feb-2011  09:30:45    58.04  1
1699118  22-Feb-2011  09:30:54    58     2
1699119  22-Feb-2011  09:30:57    58.05  1

ID 列是IDENTITY列。

我正在使用此查询来获取连续行计数为：

The ID column is an IDENTITY column.
And I'm using this query to get the consecutive row count as:

  SELECT   ID, Date_trans, Time_trans, Price
          ,ROW_NUMBER() OVER(PARTITION BY Price  ORDER BY ID) RowCount
  FROM     MyTable
  ORDER    BY ID;

我得到的 RowCount 最适合值，但某些值是错误的。例如：

The RowCount I get is right for most of the values but wrong for some values. For instance:

• ID 1699100价格58.13 –计数应为1（显示3）。


• ID 1699104价格57.96 –计数应为1（显示2）。


• ID 1699105，1699106价格57.93 –计数应为1、2（显示2、3）。

我在PostgreSQL中尝试了相同的查询并找到了相同的结果。

我上传了此处是一个csv数据示例。

I have tried the same query in PostgreSQL and found the same results.
I have uploaded a csv data sample here.

我对这种意外的分区结果感到困惑。有人可以帮我吗？

I'm stuck with such unexpected results of partition. Can anybody help me?

推荐答案

PARTITION BY 子句code> ROW_NUMBER（）函数指示它按 Price 值设置的 entire 行分区并分配行数字以 ID s的升序排列。

The PARTITION BY clause of the ROW_NUMBER() function instructs it to partition the entire row set by Price values and assign row numbers in the ascending order of IDs.

似乎您想区分任意两组行具有相同 Price 值的值，这些值由至少一行用不同的 Price 分隔。

It seems like you want to distinguish between any two groups of rows with identical Price values that are separated by at least one row with a different Price.

可能有多种方法可以实现。在SQL Server中（我认为同样适用于PostgreSQL），我将首先使用两个 ROW_NUMBER（）调用来获取其他分区条件，然后再次对行进行排名使用该标准，例如：

There may be various ways to achieve that. In SQL Server (and I think the same would work in PostgreSQL too), I would first use two ROW_NUMBER() calls to get an additional partitioning criterion, then rank rows once again using that criterion, like this:

WITH partitioned AS (
  SELECT
    ID,
    Date_trans,
    Time_trans,
    Price,
    ROW_NUMBER() OVER (                   ORDER BY ID) -
    ROW_NUMBER() OVER (PARTITION BY Price ORDER BY ID) AS PriceGroup
  FROM MyTable
)
SELECT
  ID,
  Date_trans,
  Time_trans,
  Price,
  ROW_NUMBER() OVER (PARTITION BY Price, PriceGroup ORDER BY ID) AS RowCount
FROM partitioned
ORDER BY ID
;

这里是 SQL Fiddle演示。

这篇关于ROW_NUMBER（）显示意外值的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！