如何 SELECT 区分 SQL 中的另一列，按具有 MAX（列值）的行

Question

如何Select 将另一个列引用与具有 MAX(Column) 值的行区分开来。这是我的 table:

Category |  Desc  | Total1 | Total2 |  MaxDate   | Topic
--------------------------------------------------------
   A     | A Desc |   1    |    3   | 2017-04-01 | Topic1
   A     | A Desc |   1    |    1   | 2017-05-10 | Topic2
   B     | B Desc |   1    |    1   | 2017-03-25 | Topic3

我想在 select Topic 列中获取 MaxDate 列中的参考最大值。我希望 table 像：

Category |  Desc  | Total1 | Total2 |  MaxDate   | Topic
--------------------------------------------------------
   A     | A Desc |   2    |    4   | 2017-05-10 | Topic2
   B     | B Desc |   1    |    1   | 2017-03-25 | Topic3

然后 Total1 和 Total2 是来自 SUM 行的值具有不同的

Answer 1

根据你的数据我们也可以这样实现

Declare @Table1  TABLE 
    (Category varchar(1), Descp varchar(6), Total1 int, Total2 int, MaxDate datetime, Topic varchar(6))
;

INSERT INTO @Table1
    (Category, Descp, Total1, Total2, MaxDate, Topic)
VALUES
    ('A', 'A Desc', 1, 3, '2017-04-01 00:00:00', 'Topic1'),
    ('A', 'A Desc', 1, 1, '2017-05-10 00:00:00', 'Topic2'),
    ('B', 'B Desc', 1, 1, '2017-03-25 00:00:00', 'Topic3')
;

脚本

Select TT.Category,
   TT.Descp,
   TT.Total1,
   TT.Total2,
   TT.MaxDate,
   T.Topic 
            From @Table1 T
   INNER JOIN (
   select 
        Category,Descp,
            SUM(Total1)Total1,
            SUM(Total2)Total2,
            Max(MaxDate)MaxDate 
                    from @Table1
   GROUP BY  Category,Descp )TT
   ON T.MaxDate = TT.MAXDATE

Answer 2

用户可以这样使用row_number and sum() over()

  DECLARE @SampleData AS TABLE
  (
      Category varchar(10),  [Desc]  varchar(20), Total1 int, Total2 int,  MaxDate datetime, Topic varchar(10)
  )

  INSERT INTO @SampleData VALUES
 ('A','A Desc', 1, 3, '2017-04-01', 'Topic1'),
 ('A','A Desc', 1, 1, '2017-05-10', 'Topic2'),
 ('B','B Desc', 1, 1, '2017-03-25', 'Topic3')

 ;WITH temp AS
 (
   SELECT  sd.Category, sd.MaxDate, sd.Topic, sd.[Desc], 
         row_number() OVER(PARTITION BY sd.Category ORDER BY sd.MaxDate desc) AS Rn,
         Sum(sd.Total1) OVER(PARTITION BY sd.Category ) AS Total1,
         Sum(sd.Total2) OVER(PARTITION BY sd.Category ) AS Total2
   FROM @SampleData sd
 )
 SELECT t.Category, t.[Desc], t.Total1,t.Total2, t.MaxDate, t.ToPic
 FROM temp t
 WHERE t.Rn = 1

演示 link：http://rextester.com/NQI25173

如何 SELECT 区分 SQL 中的另一列，按具有 MAX（列值）的行

How to SELECT DISTINCT another column in SQL, by rows with MAX(Column value)

sql-server

inner-join

self-join