SQL Server。CTE，如何获取最后一行编号

Posted 2023-01-27

我有一个这样的CTE。

;WITH Lastdt AS
(
    SELECT database_name, backup_finish_date,
    ROW_NUMBER() OVER (PARTITION BY database_name ORDER BY backup_finish_date, database_name) AS 'RowNumber'
    FROM bckHist
) 
SELECT database_name, backup_finish_date
FROM Lastdt
WHERE RowNumber = '7'

我如何从查询中获得数字最大的最后一行（替换硬编码7）？

答案

如果你真的只需要最后一行（从你的查询中），那么它甚至更简单（对于给定的情况）。

select database_name, max(backup_finish_date)
from bckHist
group by database_name

另一答案

我想这很简单...

;WITH Lastdt AS
(
    SELECT database_name, backup_finish_date,
    ROW_NUMBER() OVER (PARTITION BY database_name ORDER BY backup_finish_date desc, database_name) AS 'RowNumber'
    FROM bckHist
) 
SELECT database_name, backup_finish_date
FROM Lastdt
WHERE RowNumber = '1'

另一答案

试试这个。

;WITH Lastdt AS
(
    SELECT database_name, backup_finish_date,
    ROW_NUMBER() OVER (PARTITION BY database_name ORDER BY backup_finish_date, database_name) AS 'RowNumber'
    FROM bckHist
) 
SELECT TOP 1 
   database_name, backup_finish_date
FROM Lastdt
ORDER BY RowNumber DESC

基本上是这样排序的 RowNumber 降序（最大的先），只选取第一个。

另一答案

SELECT database_name, backup_finish_date FROM bckHist WHERE RowNumber = (SELECT MAX(RowNumber) FROM bckHist)