Spark SQL入门示例

首先，导入pom依赖：

<properties>
    <maven.compiler.source>8</maven.compiler.source>
    <maven.compiler.target>8</maven.compiler.target>
    <spark.version>3.1.1</spark.version>
    <spark.scala.version>2.12</spark.scala.version>
</properties>
<dependency>
    <groupId>org.apache.spark</groupId>
    <artifactId>spark-sql_${spark.scala.version}</artifactId>
    <version>${spark.version}</version>
</dependency>

只需要导入这一个坐标即可：spark-sql_${spark.scala.version}

接着编写代码：

package com.zxl.spark.sql

import org.apache.spark.sql.catalog.{Database, Table}
import org.apache.spark.{SparkConf, SparkContext}
import org.apache.spark.sql.{DataFrame, Dataset, SparkSession, catalog}

object lesson01_sql_basic {
  def main(args: Array[String]): Unit = {
    //  sql字符串 ==》 dataset 是对rdd的包装
    //  只有rdd才能触发DAGScheduler
    val conf: SparkConf = new SparkConf().setMaster("local").setAppName("testsql")
    val session: SparkSession = SparkSession.builder()
      .config(conf)
      //.enableHiveSupport()  spark sql on hive需要开启  支持ddl
      .getOrCreate()
    //可以获取到sc
    val sparkContext: SparkContext = session.sparkContext
    sparkContext.setLogLevel("ERROR")
    val dataFrame: DataFrame = session.read.json("input/json")
    //展示数据
    println(">" * 50)
    dataFrame.show()
    //展示schema
    println(">" * 50)
    dataFrame.printSchema()
    //while (true){}
    println(">" * 50)
    val databases: Dataset[Database] = session.catalog.listDatabases()
    databases.show()
    println(">" * 50)
    val tables: Dataset[Table] = session.catalog.listTables()
    tables.show()
    println(">" * 50)
    val functions: Dataset[catalog.Function] = session.catalog.listFunctions()
    functions.show()
    println(">" * 50)
    dataFrame.createTempView("abc")
    val dataFrame1: DataFrame = session.sql("select * from abc")
    dataFrame1.show()
    println(">" * 50)
    session.catalog.listTables().show()

    import scala.io.StdIn.readLine
    while (true){
      val sqlStr: String = readLine("input your sql:")
      session.sql(sqlStr).show()
    }

  }

}

执行结果演示》》