|NO.Z.00041|——————————|BigDataEnd|——|Hadoop&Spark.V02|——|Spark.v02|spark sql|sparksession|

一、Spark SQL编程

### --- sparkseeion官方地址

~~~     官方文档：http://spark.apache.org/docs/latest/sql-getting-started.html

### --- SparkSession

~~~     在 Spark 2.0 之前：
~~~     SQLContext 是创建 DataFrame 和执行 SQL 的入口
~~~     HiveContext通过Hive sql语句操作Hive数据，兼Hhive操作，HiveContext继承自SQLContext
~~~     在 Spark 2.0 之后：
~~~     将这些入口点统一到了SparkSession，SparkSession 封装了 SqlContext 及HiveContext；
~~~     实现了 SQLContext 及 HiveContext 所有功能；
~~~     通过SparkSession可以获取到SparkConetxt；

### --- sparksession实验示例

scala> import org.apache.spark.sql.SparkSession
import org.apache.spark.sql.SparkSession

scala> val spark = SparkSession
spark: org.apache.spark.sql.SparkSession.type = org.apache.spark.sql.SparkSession$@5b0af511

scala> .builder()
res0: spark.Builder = org.apache.spark.sql.SparkSession$Builder@47651c28

scala> .appName("Spark SQL basic example")
res1: spark.Builder = org.apache.spark.sql.SparkSession$Builder@47651c28

scala> .config("spark.some.config.option", "some-value")
res2: spark.Builder = org.apache.spark.sql.SparkSession$Builder@47651c28

scala> .getOrCreate()
21/10/20 14:11:13 WARN SparkSession$Builder: Using an existing SparkSession; some configuration may not take effect.
res3: org.apache.spark.sql.SparkSession = org.apache.spark.sql.SparkSession@2a292566

~~~     # For implicit conversions like converting RDDs to DataFrames

scala> import spark.implicits._
<console>:26: error: value implicits is not a member of object org.apache.spark.sql.SparkSession
       import spark.implicits._
                    ^

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Walter Savage Landor:strove with none,for none was worth my strife.Nature I loved and, next to Nature, Art:I warm'd both hands before the fire of life.It sinks, and I am ready to depart

                                                                                                                                                   ——W.S.Landor

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