How to use CROSS JOIN and CROSS APPLY in Spark SQL

问题

I am very new to Spark and Scala, I writing Spark SQL code. I am in situation to apply CROSS JOIN and CROSS APPLY in my logic. Here I will post the SQL query which I have to convert to spark SQL.

select Table1.Column1,Table2.Column2,Table3.Column3
from Table1 CROSS JOIN Table2 CROSS APPLY Table3

I need the above query to convert in to SQLContext in Spark SQL. Kindly help me. Thanks in Advance.

回答1:

First set the below property in spark conf

spark.sql.crossJoin.enabled=true

then dataFrame1.join(dataFrame2) will do Cross/Cartesian join,

we can use below query also for doing the same

sqlContext.sql("select * from table1 CROSS JOIN table2 CROSS JOIN table3...")

回答2:

Set Spark Configuration ,

var sparkConf: SparkConf = null

 sparkConf = new SparkConf()

.set("spark.sql.crossJoin.enabled", "true")

Explicit Cross Join in spark 2.x using crossJoin Method

crossJoin(right: Dataset[_]): DataFrame

var df_new = df1.crossJoin(df2);

Note : Cross joins are one of the most time consuming joins and often should be avoided.

来源：https://stackoverflow.com/questions/40763682/how-to-use-cross-join-and-cross-apply-in-spark-sql