UnionByName with the empty dataframe

 import spark.implicits._

import org.apache.spark.sql.types.

import org.apache.spark.sql._

val data = Seq(("James","Sales",34), ("Michael","Sales",56),

("Robert","Sales",30), ("Maria","Finance",24) )

val df1 = data.toDF("name","dept","age")

df1.printSchema()

val schema = StructType(

StructField("name", StringType, true) ::

StructField("dept", StringType, false) ::

StructField("age", IntegerType, false) :: Nil)

val df = spark.createDataFrame(spark.sparkContext.emptyRDD[Row], schema)

val merged_df = df1.unionByName(df)

merged_df.show(false)

val merged_df2 = df.unionByName(df1)

merged_df2.show(false)