Spark_SQL上机实验

目录

• 实验目的：
• 实验要求：
• 实验方案

实验目的：

1、通过实验掌握Spark SQL的基本编程方法；

2、熟悉RDD到DataFrame的转化方法；

实验要求：

按实验要求完成实验。

实验方案

1．Spark SQL基本操作

Win10更新后，linux系统的Hadoop环境已崩溃，故在此使用datadatabricks

将下列JSON格式数据复制到Linux系统中，并保存命名为employee.json。

{ "id":1 , "name":" Ella" , "age":36 }

{ "id":2, "name":"Bob","age":29 }

{ "id":3 , "name":"Jack","age":29 }

{ "id":4 , "name":"Jim","age":28 }

{ "id":4 , "name":"Jim","age":28 }

{ "id":5 , "name":"Damon" }

{ "id":5 , "name":"Damon" }

#读取json文件

\# File location and type

file_location = "/FileStore/tables/employee.json"

file_type = "json"

 

\# CSV options

infer_schema = "false"

first_row_is_header = "false"

delimiter = ","

 

\# The applied options are for CSV files. For other file types, these will be ignored.

df = spark.read.format(file_type) \

 .option("inferSchema", infer_schema) \

 .option("header", first_row_is_header) \

 .option("sep", delimiter) \

 .load(file_location)

 

display(df)                 #打印出文件


# 创建employee临时表

df.registerTempTable("employee") 

1. 查询所有数据；

sqlDF_01 = spark.sql("SELECT * FROM employee");

sqlDF_01.show();

]

2.查询所有的数据,并去重

sqlDF_02 = spark.sql("SELECT DISTINCT * FROM employee");

sqlDF_02.show();


3.查询所有的数据,打印去除id字段（这里只查询了name age）

sqlDF_03 = spark.sql("SELECT name,age FROM employee");

sqlDF_03.show();     


4.查询age>30的数据

sqlDF_04 = spark.sql("SELECT * FROM employee WHERE age > 30")

sqlDF_04.show();

​

]

5.age分组

sqlDF_05 = spark.sql("SELECT * FROM employee GROUP BY age");

sqlDF_05.show();

]

6.name升序

sqlDF_06 = spark.sql("SELECT * FROM employee ORDER BY name")

sqlDF_06.show();

]

​

7.前三行

sqlDF_07 = spark.sql("SELECT * FROM employee")

sqlDF_07.show(3);


8.修改列名,name改成uersname

sqlDF_08 = spark.sql("SELECT name AS username FROM employee")

sqlDF_08.show();


9.查询age平均值

sqlDF_09 = spark.sql("SELECT AVG(age) AS ageAverage FROM employee")

sqlDF_09.show();


10.查询age最小值

sqlDF_10 = spark.sql("SELECT MIN(age) AS ageAverage FROM employee")

sqlDF_10.show();

]

2．编程实现将RDD转换为DataFrame. （Scala）

import org.apache.spark.sql.catalyst.encoders.ExpressionEncoder

import org.apache.spark.sql.Encoder

import spark.implicits._ //导入包，支持把一个RDD隐式转换为一个DataFrame

case class students_data(id:Int,name:String,gender:String,age:Int,course_id:Int,score:Double,classes:String) //定义一个case class

val stuDF = spark.sparkContext.textFile("/FileStore/tables/students_data-7.txt").map(_.split(",")).map(t => students_data(t(0).trim.toInt, t(1), t(2), t(3).trim.toInt, t(4).trim.toInt, t(5).trim.toDouble, t(6))).toDF()

stuDF.createOrReplaceTempView("stu") //必须注册为临时表才能供下面的查询

val stuRDD = spark.sql("select * from stu")//最终生成一个DataFrame

stuRDD.show()

]