从查询结果中选择？

Question

我有一个类似这样的查询：

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

它返回以下内容：

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

我需要获取表格Weighings中，列Weight_kg在返回值FirstDate和LastDate之间的数值，以便产生如下结果：

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

我已经尝试了所有可能的组合，但无法解决它，有任何想法吗？ 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

- Myles Gray

---

你能添加一些示例行的表模式吗？ - Utku Yıldırım

Answer 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

在这里尝试：https://data.stackexchange.com/stackoverflow/q/118518/

- Mikael Eriksson

Answer 2

你可以使用RANK..OVER语句（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

- Adilson de Almeida Jr

Answer 3

你有两种可能性。

如果你想要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，请使用“select”语句。

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

- Míla Mrvík

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你没有在这里创建一个“临时”表。 - Ash Burlaczenko