从查询结果中选择？答案

【问题标题】：Select from results of query?从查询结果中选择？
【发布时间】：2012-01-03 00:00:06
【问题描述】：

我有一个这样的查询：

SELECT Weighings.Member, MIN(Sessions.DateTime) AS FirstDate, MAX(Sessions.DateTime) AS LastDate
FROM Weighings AS Weighings INNER JOIN
     Sessions ON Sessions.SessionGUID = Weighings.Session
WHERE     (Sessions.DateTime >= '01/01/2011')
GROUP BY Weighings.Member
ORDER BY Weighings.Member

它返回这个：

Member | FirstDate | LastDate
Blah   | 01/01/11  | 06/07/11
Blah2  | 02/03/11  | 05/07/11

我需要在表Weighings 中为返回值FirstDate 和LastDate 获取单元格Weight_kg 的值，以给出如下结果：

Member | FirstWeight | LastWeight
Blah   | 150Kg       | 60KG
Blah2  | 70Kg        | 72KG

我已经尝试了所有的组合，但无法解决，有什么想法吗？

编辑

表格：

Sessions
______________________
SessionGUID | DateTime
----------------------
12432524325 | 01/01/11
12432524324 | 01/08/11
12432524323 | 01/15/11
34257473563 | 03/05/11
43634574545 | 06/07/11

Weighings
_____________________________________
Member      | Session     | Weight_kg
-------------------------------------
vffd8fdg87f | 12432524325 | 150
vffd8fdg87f | 12432524324 | 120
vffd8fdg87f | 12432524323 | 110
ddffv89sdv8 | 34257473563 | 124
32878vfdsv8 | 43634574545 | 75

【问题讨论】：

您可以添加带有一些示例行的表架构吗？

标签： sql database sql-server-2005 tsql

【解决方案1】：

;with C as
(
  select W.Member,
         W.Weight_kg,
         row_number() over(partition by W.Member order by S.datetime desc) as rnLast,
         row_number() over(partition by W.Member order by S.datetime asc) as rnFirst
  from Weighings as W
    inner join Sessions as S
      on S.sessionguid = W.Session and
         S.DateTime >= '20110101'
)
select CF.Member,
       CF.Weight_kg as FirstWeight,
       CL.Weight_kg as LastWeigth
from C as CF
  inner join C as CL
    on CF.Member = CL.Member
where CF.rnFirst = 1 and
      CL.rnLast = 1

在这里试试：https://data.stackexchange.com/stackoverflow/q/118518/

【讨论】：

【解决方案2】：

您可以使用 RANK..OVER stmt（仅适用于 SQL 2k5+）

select fw.Member, st.Weight, en.Weight
from
(
    select Member, Weight, RANK() OVER(PARTITION BY Member ORDER BY Weight) rnk
    from Weighings
) st
inner join 
(
    select Member, Weight, RANK() OVER(PARTITION BY Member ORDER BY WeightDESC) rnk
    from Weighings
) en on en.Member= st.Member and st.rnk = 1 and en.rnk = 1

【讨论】：

【解决方案3】：

你有两种可能。

如果您想多次重复使用第一个 SELECT，我建议创建临时表

CREATE TEMPORARY TABLE `tmpTable` AS SELECT /*the first select*/ ;

/*and then*/

SELECT * FROM `tmpTable` /*the second select from the first select*/

如果您只需要第一次选择一次

SELECT first.* 
FROM (SELECT /*the first select*/) AS first

【讨论】：

您没有在此处创建Temporary 表。