使用 ROW_NUMBER 和 PARTITION BY 获取第一行和最后一行

Question

样例输入

Name | Value | Timestamp
-----|-------|-----------------
One  | 1     | 2016-01-01 02:00
Two  | 3     | 2016-01-01 03:00
One  | 2     | 2016-01-02 02:00
Two  | 4     | 2016-01-03 04:00

期望的输出

Name | Value | EarliestTimestamp | LatestTimestamp
-----|-------|-------------------|-----------------
One  | 2     | 2016-01-01 02:00  | 2016-01-02 02:00
Two  | 4     | 2016-01-01 03:00  | 2016-01-03 04:00

尝试查询

我正在尝试使用 ROW_NUMBER() 和 PARTITION BY 获取最新的 Name 和 Value，但我还想得到最早和最晚的 Timestamp 值：

SELECT
    t.Name,
    t.Value,
    t.????????? AS EarliestTimestamp,
    t.Timestamp AS LatestTimestamp
FROM 
    (SELECT
        ROW_NUMBER() OVER (PARTITION BY Name ORDER BY TIMESTAMP DESC) AS RowNumber,
        Name,
        Value
        Timestamp) t
WHERE t.RowNumber = 1

- Muhammad Rehan Saeed

Answer 1

这可以使用窗口函数min和max来完成。

select distinct name, 
min(timestamp) over(partition by name), max(timestamp) over(partition by name)
from tablename

Example

Edit: Based on the comments

select t.name,t.value,t1.earliest,t1.latest
from t 
join (select distinct name, 
      min(tm) over(partition by name) earliest, max(tm) over(partition by name) latest
      from t) t1 on t1.name = t.name and t1.latest = t.tm

编辑：另一种方法是使用 first_value 窗口函数，这将消除子查询和连接的需求。

select distinct
name, 
first_value(value) over(partition by name order by timestamp desc) as latest_value,
min(tm) over(partition by name) earliest,
-- or first_value can be used 
-- first_value(timestamp) over(partition by name order by timestamp)
max(tm) over(partition by name) latest
-- or first_value can be used
-- first_value(timestamp) over(partition by name order by timestamp desc)
from t

- Vamsi Prabhala

---

请注意，此查询仅在“value”随时间增长时有效。如果我们将OP示例的第一行中的“value”从1更改为10，则此查询将产生错误的结果。 - gofr1

@gofr1 是的。你可能想要使用的是 last_value(value) over (partition by name order by timestamp)。 - Chitharanjan Das

Answer 2

您可以使用 MIN 和 MAX 函数 + OUTER APPLY：

SELECT  t.Name, 
        p.[Value],
        MIN(t.[Timestamp]) as EarliestTimestamp ,
        MAX(t.[Timestamp]) as LatestTimestamp
FROM Table1 t
OUTER APPLY (SELECT TOP 1 * FROM Table1 WHERE t.Name = Name ORDER BY [Timestamp] DESC) p
GROUP BY t.Name, p.[Value]

输出：

Name    Value   EarliestTimestamp   LatestTimestamp
One     2       2016-01-01 02:00    2016-01-02 02:00
Two     4       2016-01-01 03:00    2016-01-03 04:00

- gofr1

Answer 3

如果我正确理解了你的问题，这里有一个选项可以使用row_number函数两次。然后为了让它们在同一行上，您可以使用条件聚合。这应该很接近：

SELECT
    t.Name,
    t.Value,
    max(case when t.minrn = 1 then t.timestamp end) AS EarliestTimestamp,
    max(case when t.maxrn = 1 then t.timestamp end) AS LatestTimestamp
FROM 
    (SELECT
        ROW_NUMBER() OVER (PARTITION BY Name ORDER BY TIMESTAMP) as minrn,
        ROW_NUMBER() OVER (PARTITION BY Name ORDER BY TIMESTAMP DESC) as maxrn,
        Name,
        Value
        Timestamp
     FROM YourTable) t
WHERE t.minrn = 1 or t.maxrn = 1
GROUP BY t.Name, t.Value

- sgeddes

Answer 4

除了ROW_NUMBER()列之外，还需要使用 MIN(Timestamp) OVER (PARTITION BY Name)，如下所示：

SELECT
    t.Name,
    t.Value,
    t.EarliestTimestamp AS EarliestTimestamp,
    t.Timestamp AS LatestTimestamp
FROM 
    (SELECT
        ROW_NUMBER() OVER (PARTITION BY Name ORDER BY TIMESTAMP DESC) AS RowNumber,
        MIN(Timestamp) OVER (PARTITION BY Name) AS EarliestTimestamp,
        ^^
        Name,
        Value
        Timestamp) t
WHERE t.RowNumber = 1

- Chitharanjan Das

Answer 5

如果我理解你的问题，可以使用row_number()函数，如下所示：

SELECT  
    t.Name,  
    t.Value,  
    min(t.Timestamp) Over (Partition by name) As EarliestTimestamp,  
    t.Timestamp AS LatestTimestamp  
FROM   
    (SELECT ROW_NUMBER() OVER (PARTITION BY Name ORDER BY TIMESTAMP DESC) AS     RowNumber,  
        Name,  
        Value,  
        Timestamp) t  
WHERE t.RowNumber = 1  
Group By t.Name, t.Value, t.TimeStamp

- Aldo López

Answer 6

保持简单。

select 
    t.Name, 
    MAX(t.Value), 
    MIN(t.Timestamp), 
    MAX(t.Timestamp) 
FROM 
    t
group by 
    t.Name

- NEER