Scala如何匹配两个dfs，如果数学，然后更新第一个df中的键，并从所需df中选择所有列

import org.apache.spark.sql.{DataFrame, SparkSession}
import org.apache.spark.sql.functions._

val spark = SparkSession.builder()
  .appName("DataFrame Join")
  .master("local")
  .getOrCreate()

val df1 = spark.createDataFrame(Seq(
  (1, "John"),
  (2, "Mike"),
  (3, "Anna")
)).toDF("id", "name")

val df2 = spark.createDataFrame(Seq(
  (1, "New York"),
  (2, "London"),
  (4, "Paris")
)).toDF("id", "city")

val joinedDF = df1.join(df2, Seq("id"), "left_outer")
  .withColumn("name", when(col("city").isNull, col("name")).otherwise(col("city")))
  .drop("city")

joinedDF.show()