join two dataframe without having common column spark, scala

问题

I have two dataframes which has different types of columns. I need to join those two different dataframe. Please refer the below example

val df1 has
Customer_name 
Customer_phone
Customer_age

val df2 has
Order_name
Order_ID

These two dataframe doesn't have any common column. Number of rows and Number of columns in the two dataframes also differs. I tried to insert a new dummy column to increase the row_index value as below val dfr=df1.withColumn("row_index",monotonically_increasing_id()).

But As i am using spark-2, monotonically_increasing_id method is not supporting for me. Is there any way to join two dataframe. So that i can create the value of two dataframe in a single sheet of excel file.

For example

val df1:
Customer_name  Customer_phone  Customer_age
karti           9685684551     24      
raja            8595456552     22

val df2:
Order_name Order_ID
watch       1
cattoy     2

My final excel sheet should be like this:

Customer_name  Customer_phone  Customer_age   Order_name  Order_ID

karti          9685684551      24             watch        1

raja           8595456552      22             cattoy      2

回答1:

monotonically_increasing_id() is increasing and unique but not consecutive.

You can use zipWithIndex by converting to rdd and reconstructing Dataframe with the same schema for both dataframe.

import spark.implicits._


val df1 = Seq(
  ("karti", "9685684551", 24),
  ("raja", "8595456552", 22)
).toDF("Customer_name", "Customer_phone", "Customer_age")


val df2 = Seq(
  ("watch", 1),
  ("cattoy", 2)
).toDF("Order_name", "Order_ID")

val df11 = spark.sqlContext.createDataFrame(
  df1.rdd.zipWithIndex.map {
    case (row, index) => Row.fromSeq(row.toSeq :+ index)
  },
  // Create schema for index column
  StructType(df1.schema.fields :+ StructField("index", LongType, false))
)


val df22 = spark.sqlContext.createDataFrame(
  df2.rdd.zipWithIndex.map {
    case (row, index) => Row.fromSeq(row.toSeq :+ index)
  },
  // Create schema for index column
  StructType(df2.schema.fields :+ StructField("index", LongType, false))
)

Now join the final dataframes

df11.join(df22, Seq("index")).drop("index")

Output:

+-------------+--------------+------------+----------+--------+
|Customer_name|Customer_phone|Customer_age|Order_name|Order_ID|
+-------------+--------------+------------+----------+--------+
|karti        |9685684551    |24          |watch     |1       |
|raja         |8595456552    |22          |cattoy    |2       |
+-------------+--------------+------------+----------+--------+

回答2:

add an index column to both dataframe using the below code

df1.withColumn("id1",monotonicallyIncreasingId)
df2.withColumn("id2",monotonicallyIncreasingId)

then join both the dataframes using the below code and drop the index column

df1.join(df2,col("id1")===col("id2"),"inner")
   .drop("id1","id2")

来源：https://stackoverflow.com/questions/49738694/join-two-dataframe-without-having-common-column-spark-scala

标签

scala

apache-spark

spark-submit

apache-spark-function