package com.ws.sparksql
import org.apache.spark.rdd.RDD
import org.apache.spark.sql.{DataFrame, SQLContext}
import org.apache.spark.{SparkConf, SparkContext}

/**
  * spark sql版本 1.1x
  * spark sql 第一個demo
  */
object SparkSqlDemo {

  def main(args: Array[String]): Unit = {

    val conf = new SparkConf().setAppName("SparkSqlDemo").setMaster("local[2]")

    val sc = new SparkContext(conf)
    //建立一個sparksql例項
    val sQLContext = new SQLContext(sc)

    val dataRdd: RDD[String] = sc.textFile("hdfs://hadoop-01:9000/student")

    val studentRdd: RDD[Student] = dataRdd.map(line => {

      val strArr: Array[String] = line.split(",")
      val id = strArr(0).toLong
      val name = strArr(1)
      val age = strArr(2).toInt
      val score = strArr(3).toInt
      Student(id, name, age, score)
    })

    import sQLContext.implicits._
    //把普通RDD轉換成特殊的RDD，變成dataFrame
    val sdf: DataFrame = studentRdd.toDF

    //將dataFrame註冊一個表
    sdf.registerTempTable("t_student")

    //寫sprak sql,本質也是Transformation
    val result: DataFrame = sQLContext.sql("select * from t_student order by score desc , age asc")

    //觸發Action操作，展示結果
    result.show()

    sc.stop()
  }
}

case class Student(id: Long, name: String, age: Int, score: Int)
 

結果 ：

+---+----+---+-----+
| id|name|age|score|
+---+----+---+-----+
|  1|  張三| 18|  150|
|  2|  李四| 19|  150|
|  3|  王五| 20|   98|
|  4|  趙六| 17|   88|
+---+----+---+-----+