scala程序搜索最新的值
我想根据下面的配置单元sql创建df:scala程序搜索最新的值,scala,apache-spark,bigdata,Scala,Apache Spark,Bigdata,我想根据下面的配置单元sql创建df: WITH FILTERED_table1 AS (select * , row_number() over (partition by key_timestamp order by datime DESC) rn FROM table1) scala function: import org.apache.spark.sql.expressions.Window import org.apache.spark.sql.functions._ import
WITH FILTERED_table1 AS (select *
, row_number() over (partition by key_timestamp order by datime DESC) rn
FROM table1)
scala function:
import org.apache.spark.sql.expressions.Window
import org.apache.spark.sql.functions._
import org.apache.spark.sql.SparkSession
val table1 = Window.partitionBy($"key_timestamp").orderBy($"datime".desc)
我查看了窗口函数,这就是我能想到的,我不知道如何在scala函数中编写它,因为我对scala非常陌生。如何从sql use scala函数返回df?
如有任何建议,将不胜感激 您的窗口规格是正确的。使用虚拟数据集,首先将原始配置单元表加载到数据帧中:
val df = spark.sql("""select * from table1""")
df.show
// +-------------+-------------------+
// |key_timestamp| datime|
// +-------------+-------------------+
// | 1|2018-06-01 00:00:00|
// | 1|2018-07-01 00:00:00|
// | 2|2018-05-01 00:00:00|
// | 2|2018-07-01 00:00:00|
// | 2|2018-06-01 00:00:00|
// +-------------+-------------------+
要将窗口规范上的窗口函数行_编号应用于数据帧,请使用withColumn生成新列以捕获函数结果:
import org.apache.spark.sql.functions._
import org.apache.spark.sql.expressions.Window
val window = Window.partitionBy($"key_timestamp").orderBy($"datime".desc)
val resultDF = df.withColumn("rn", row_number.over(window))
resultDF.show
// +-------------+-------------------+---+
// |key_timestamp| datime| rn|
// +-------------+-------------------+---+
// | 1|2018-07-01 00:00:00| 1|
// | 1|2018-06-01 00:00:00| 2|
// | 2|2018-07-01 00:00:00| 1|
// | 2|2018-06-01 00:00:00| 2|
// | 2|2018-05-01 00:00:00| 3|
// +-------------+-------------------+---+
要进行验证,请针对表1运行SQL,您应该会得到相同的结果:
spark.sql("""
select *, row_number() over
(partition by key_timestamp order by datime desc) rn
from table1
""").show