[英]Getting the First and Last Row Using ROW_NUMBER and PARTITION BY
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
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
我試圖使用ROW_NUMBER()
和PARTITION BY
來獲取最新的Name
和Value
但我還想要最早和最新的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
這可以使用窗口函數min
和max
來完成。
select distinct name,
min(timestamp) over(partition by name), max(timestamp) over(partition by name)
from tablename
編輯:根據評論
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
編輯:另一種方法是使用first_value
窗口函數,這將消除對子查詢和連接的需要。
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
你可以使用MIN和MAX函數+ 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]
輸出:
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
除了ROW_NUMBER()
列之外,還使用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
如果我正確理解你的問題,這里有兩個使用row_number
函數的選項。 然后,為了使它們在同一行,您可以使用conditional aggregation
。
這應該是接近的:
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
想想簡單。
select
t.Name,
MAX(t.Value),
MIN(t.Timestamp),
MAX(t.Timestamp)
FROM
t
group by
t.Name
如果我理解你的問題,請使用row_number()
函數,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
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