Question

所以，我在这一个人的头上碰到了我的头...... 我有一个表（几百万行）看起来像这样：

ID  Time            Area    Name
1   2017-01-01 01:42    21  Test
1   2017-01-02 02:13    21  Test
1   2017-02-01 12:45    30  N/A
1   2017-03-12 02:23    41  N/A
2   2017-02-15 04:25    20  N/A

我想运行一个查询，选择某个ID的最新区域; 结果是这样的：

ID  Time            Area    Name
1   2017-01-02 02:13    21  Test
1   2017-02-01 12:45    30  N/A
1   2017-03-12 02:23    41  N/A

select max(Time),
"of every area"
from TABLE
where ID = 1

如果有人能给我一个线索，那就太棒了！

Answer 1

您可以使用ROW_NUMBER：

SELECT * FROM (
  SELECT *, ROW_NUMBER() OVER(PARTITION BY Area ORDER BY Time DESC) AS rn
  FROM table) sub
WHERE rn = 1

Answer 2

又一个选项（没有子查询和/或额外字段）

示例

Select Top 1 with Ties * From YourTable Where ID =1 Order By Row_Number() over (Partition By Area Order By [Time] Desc)

<强>返回

ID Time Area Name 1 2017-01-02 02:13:00.000 21 Test 1 2017-02-01 12:45:00.000 30 N/A 1 2017-03-12 02:23:00.000 41 N/A

Answer 3

lad2025是正确的。

要更具体地说明您对特定ID的要求，请使用

myChatHub

使用CTE，您可以使用与

相同的内容

SELECT * FROM (
   SELECT *, ROW_NUMBER() OVER(PARTITION BY Area ORDER BY Time DESC) AS rn
   FROM table WHERE ID=1) sub
WHERE rn = 1

Answer 4

或者更老的学校方法是在派生表中使用GROUP BY

SELECT Test.* FROM dbo.testTable Test
INNER JOIN (
    SELECT Id, MAX(Time) Time, Area 
    FROM dbo.testTable
    GROUP BY Id, Area 
) TestMax ON TestMax.Id = Test.Id AND TestMax.Time = Test.Time AND 
TestMax.Area = Test.Area
ORDER BY Test.Id, Test.Area;

MSSQL - 选择表中最近出现的几行

4 个答案: