Question

在MonetDB中工作时，我有一个包含时间值的“入口时间”列。我有：

   select "minute"(entrytime) as unitTime, period
   from schema1.zones
   where date1 >=  eDate and date1 <= xDate and id=256
   group by  unitTime, period

但是我想在15分钟的边界上对结果进行分组，然后返回15分钟块的最大'周期'值，任何想法？

感谢。

Answer 1

这是R解决方案的示例。我认为您只需要将您的入场时间列转换为您想要的间隔时间？然后你可以用MAX（）？

运行一个组

# run this line once
# install.packages( "MonetDBLite" )

library(DBI)

x <- data.frame( entrytime = sample( 1:1000 , 10000 , replace = TRUE ) , period = sample( 1:10 , 10000 , replace = TRUE ) )

head( x )

x$intervals <- findInterval( x$entrytime , seq( 0 , 1000 , by = 15 ) )

db <- dbConnect( MonetDBLite::MonetDBLite() )

dbWriteTable( db , 'x' , x )

# max period for distinct minutes
head( dbGetQuery( db , "SELECT entrytime , MAX( period ) FROM x GROUP BY entrytime" ) )

# max period for 15 minute intervals
head( dbGetQuery( db , "SELECT intervals , MAX( period ) FROM x GROUP BY intervals" ) )

monetdb，group by

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