Question

我有一个表，其中包含一些借给用户的计算机列表。每次退回机器时都会输入一个条目。我使用以下语句按用户，机器＃，日期和操作

返回列表

SELECT Name, Asset#, Date, InOut
FROM Table
ORDER BY Asset#, date asc

返回

Name      Asset#       Date        InOut
Jimmy     BER210    2009-05-08      out
Jimmy     BER210    2009-06-08      in
Jimmy     BER210    2009-07-08      out
Sam       BER220    2009-05-08      out
Sam       BER220    2009-06-08      In
Jack      BER230    2009-05-08      out
Jack      BER230    2009-06-08      In
Jack      BER230    2009-07-08      out

我正在寻找帮助修改该查询以仅返回最近的条目，并且仅在该机器当前已退出时。

提前感谢您提供的任何帮助！

Answer 1

您可以使用inner join过滤掉每台计算机的旧行。获得最新行后，可以使用where选择“out”的计算机。

select  Name, Asset#, Date, InOut
from    Table t
join    (
        select  Asset#
        ,       max(Date) as MaxDate
        from    Table
        group by
                Asset#
        ) filter
on      filter.Asset# = t.Asset#
        and filter.MaxDate = t.Date
where   t.InOut = 'Out'

Answer 2

select Name, Asset#, Date, InOut
 from Table
   natural join (
    select Asset#, max(Date) as Date
    from Table
    group by Asset#
  )
where InOut = 'out'
order by date desc

固定

Answer 3

在SQLServer中

SELECT TOP 1 Name, Asset#, Date, InOut
FROM Table
WHERE InOut = 'out'
ORDER BY Date DESC

在MySQL中

SELECT Name, Asset#, Date, InOut
FROM Table
WHERE InOut = 'out'
ORDER BY Date DESC
LIMIT 1

Answer 4

SELECT Name, Asset#, Date, InOut
FROM Table o
WHERE Date = (select max(Date) from 
              Table i 
              where i.Asset# = o.Asset#
             )
)
where o.in_out = 'out'
ORDER BY Asset#, date asc

修改根据评论将i.in_out更改为o.in_out。

Answer 5

SELECT Name，Asset＃，Date，InPut

FROM表WHERE InOut ='out'ORDER BY date desc

选择组中的条件数据

5 个答案: