查找两个日期之间的中位数 SQL Server 2008

Question

我正在寻找一种方法来获取一堆开始日期和结束日期（很多和很多日期）的中位数。但是，它将特定于各种“发票编号”。请参阅下面的示例数据。

 invoice_no    invoice start date      invoice end date
 4006            11/14/2001               12/15/2004
 20071           11/29/2001               02/01/2003
 19893           11/30/2001               12/02/2001
 19894           11/30/2001               12/04/2001
 004             10/22/2002               10/31/2002
 004             12/02/2002               10/31/2002
 004             01/19/2002               10/31/2002
 004             05/10/2002               10/31/2002

求开始日期和结束日期之间的中位数。

对于只显示一次的发票，中位数将是该特定 invoice_no 的开始日期和结束日期之间的任何值。但是，许多情况下会显示发票“004”。它会在不同的日期重复很多次——但这里的概念仍然相同。需要找到两个日期之间的中位数，但仍需要根据该发票编号显示。

尽可能过滤数据。我意识到我也可以做 WHERE STATUS 'REJECTED' 并且它也应该有助于避免很多不必要的日期。另外，我只想在几个月之间过滤，所以我也添加了 BETWEEN DATETIME。

到目前为止的代码（但不工作......如果有 1 个日期列，这种逻辑似乎工作，但现在我们正在处理两个日期，所以我不确定）：

 与
          时间间隔
    (
        选择发票编号，
        invoice_start_date、invoice_end_date、check_date、status_code、
        cast(count(*) OVER (PARTITION BY invoice_no) as float) 总计，
        row_number() OVER (PARTITION BY invoice_no ORDER BY
        invoice_start_date, invoice_end_date, check_date) AS rn

    FROM    INVOICE_HEADER INNER JOIN
   INVOICE_HEADER_CUSTOM ON INVOICE_HEADER.invoice_id 
    = INVOICE_HEADER_CUSTOM.invoice_id

    WHERE status_code <> 'REJECTED' AND 
    Check_Date BETWEEN CONVERT(DATETIME, '2014-12-01 00:00:00', 102) 
    AND CONVERT(DATETIME, '2014-12-31 00:00:00', 102)
)

    SELECT *
    FROM tmp
    WHERE (total / 2.0 - 1) < rn and rn < (total / 2.0 + 1) 

Answer 1

如果您指的是开始日期和结束日期的集合，则将它们放在一列中：

WITH t AS (
       SELECT invoice_no, invoice_start_date, invoice_end_date, check_date, status_code,
       FROM INVOICE_HEADER INNER JOIN
            INVOICE_HEADER_CUSTOM
            ON INVOICE_HEADER.invoice_id = INVOICE_HEADER_CUSTOM.invoice_id
       WHERE status_code <> 'REJECTED' AND 
             Check_Date BETWEEN CONVERT(DATETIME, '2014-12-01 00:00:00', 102) AND
             CONVERT(DATETIME, '2014-12-31 00:00:00', 102)
     ), 
     t2 as (
      select d, row_number() over (order by d) as seqnum,
             count(*) over () as cnt
      from (select invoice_start_date as d from t
            union all
            select invoice_end_date as d from t
           ) t
     )
select dateadd(day, datediff(hour, min(d), max(d)) / 2.0, min(d))
from t2
where 2 * seqnum in (cnt, cnt + 1, cnt + 2);

Answer 2

好的...试试this page上的查询：

SELECT @Median = AVG(1.0 * val)
FROM 
(
  SELECT val, 
     c  = COUNT(*) OVER (),
     rn = ROW_NUMBER() OVER (ORDER BY val)
  FROM dbo.EvenRows
) AS x
WHERE rn IN ((c + 1)/2, (c + 2)/2);