sparkSQL獲取DataFrame的幾種方式

sparkSQL獲取DataFrame的幾種方式

1. on a specific DataFrame.

import org.apache.spark.sql.Column

df("columnName") 

2.  A generic column no yet associated with a DataFrame.

import org.apache.spark.sql.functions._

col("columnName")

3. Scala short hand for a named column.

import spark.implicits._
df.select($"name")

4. Scala short hand for a named column.

import spark.implicits._
df.select('name)