相关疑难解决方法(0)

假设我有这个表:

select * from window_test;

 k | v
---+---
 a | 1
 a | 2
 b | 3
 a | 4

最终我想得到:

 k | min_v | max_v
---+-------+-------
 a | 1     | 2
 b | 3     | 3
 a | 4     | 4

但我会很高兴得到这个(因为我可以很容易地过滤它distinct):

 k | min_v | max_v
---+-------+-------
 a | 1     | 2
 a | 1     | 2
 b | 3     | 3
 a | 4     | 4

使用PostgreSQL 9.1+窗口函数可以实现这一点吗？我试图了解我是否可以使用单独的分区来处理k=a此示例中的第一次和最后一次(按顺序排列v).

我有一个查询,使用FULL JOIN需要2.5秒,使用INNER,RIGHT或LEFT JOIN需要40秒.

这是查询.子查询(完成两次)只需要1.3秒.

SELECT T1.[time], T1.Total, T1.rn, T2.[time], T2.Total, T2.rn
FROM
(
select [time], MAX(ComputedValue) as Total, row_number() over (order by [time]) as rn
FROM
(
    select SUBSTRING(CONVERT(CHAR(10), IntervalStartTime, 108), 0, 6) as [time], ComputedValue
    from LoadTestTransactionSample
    where LoadTestRunId=285
    and CounterName='Total Transactions' 
    and TransactionName='Export'
) foo
group by [time]
) T1
_____ JOIN
(
select [time], MAX(ComputedValue) as Total, row_number() over (order by [time]) as rn
FROM
(
    select SUBSTRING(CONVERT(CHAR(10), IntervalStartTime, 108), 0, 6) as [time], ComputedValue
    from LoadTestTransactionSample …