error: overloaded method value select with alternatives:

scala> df.select("dest_country_name",col("dest_country_name")).show

:26: error: overloaded method value select with alternatives:

U1, U2\](c1: org.apache.spark.sql.TypedColumn\[org.apache.spark.sql.Row,U1\], c2: org.apache.spark.sql.TypedColumn\[org.apache.spark.sql.Row,U2\])org.apache.spark.sql.Dataset\[(U1, U2)

(col: String,cols: String*)org.apache.spark.sql.DataFrame

(cols: org.apache.spark.sql.Column*)org.apache.spark.sql.DataFrame

cannot be applied to (String, org.apache.spark.sql.Column)

df.select("dest_country_name",col("dest_country_name")).show

^

scala>

注意在Spark的Scala API中，select方法存在重载限制，Spark的select方法不支持混合传入String和Column类型的参数，它只接受以下两种情况：

1. 全部传入String类型
2. 全部传入Column类型