Spark2.x学习笔记：Spark SQL的SQL

Spark SQL所支持的SQL语法

select [distinct] [column names]|[wildcard]
from tableName
[join clause tableName on join condition]
[where condition]
[group by column name]
[having conditions]
[order by column names [asc|desc]]

如果只用join进行查询，则支持的语法为：

select statement
from statement
[join | inner join | left join | left semi join | left outer join | right join |right outer join | full join | full outer join]
on join condition

Spark SQL的SQL的框架

与Hive Metastore结合

（1）Spark要能找到HDFS和Hive的配置文件

• 第1种方法：可以直接将core-site.xml、hdfs-site.xml和hive-site.xml复制到Spark安装目录下的conf目录中。该方法存在一个缺陷，如果HDFS或Hive的配置修改了，则需要手动修改Spark对应的配置文件。
• 第2种方法：在Spark配置文件中指定Hadoop配置文件目录

（2）Spark SQL与Hive Metastore结合，直接使用spark.sql(“select … from table where …”)

15.4 实例演示

（1）spark-shell

[root@node1 ~]# spark-shell
// :: WARN NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
Spark context Web UI available at http://192.168.80.131:4040
Spark context available as 'sc' (master = local[*], app id = local-).
Spark session available as 'spark'.
Welcome to
      ____              __
     / __/__  ___ _____/ /__
    _\ \/ _ \/ _ `/ __/  '_/
   /___/ .__/\_,_/_/ /_/\_\   version 2.2.
      /_/

Using Scala version 2.11. (Java HotSpot(TM) -Bit Server VM, Java 1.8.0_112)
Type in expressions to have them evaluated.
Type :help for more information.

scala> spark.sql("show databases").show
+------------+
|databaseName|
+------------+
|     default|
|        test|
+------------+

scala> spark.sql("show tables").show
+--------+---------+-----------+
|database|tableName|isTemporary|
+--------+---------+-----------+
| default|  copyemp|      false|
| default|     demo|      false|
| default|     dept|      false|
| default|     dual|      false|
| default|      emp|      false|
| default|   empbak|      false|
| default|employees|      false|
| default|     mytb|      false|
| default|    users|      false|
+--------+---------+-----------+

scala> spark.sql("select * from emp").show
+----+------+---------+----+----------+------+------+----+
| eid| ename|      job| mgr|  hiredate|   sal|  comm| did|
+----+------+---------+----+----------+------+------+----+
|| CLARK|  MANAGER||--|2450.0|   0.0|  |
||  KING|PRESIDENT|   |--|5000.0|   0.0|  |
||MILLER|    CLERK||--|1300.0|   0.0|  |
|| SMITH|    CLERK||--| 800.0|   0.0|  |
|| JONES|  MANAGER||--|2975.0|   0.0|  |
||  FORD|  ANALYST||--|3000.0|   0.0|  |
|| ALLEN| SALESMAN||--|1600.0| 300.0|  |
||  WARD| SALESMAN||--|1250.0| 500.0|  |
||MARTIN| SALESMAN||--|1250.0|1400.0|  |
|| BLAKE|  MANAGER||--|2850.0|   0.0|  |
||TURNER| SALESMAN||--|1500.0|   0.0|  |
|| JAMES|    CLERK||--| 950.0|   0.0|  |
||HADRON|     null|null|--|6666.0|  null|null|
+----+------+---------+----+----------+------+------+----+

（2）spark-sql

[root@node1 ~]# spark-sql
// :: WARN NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
// :: WARN ObjectStore: Version information not found in metastore. hive.metastore.schema.verification is not enabled so recording the schema version 1.2.
// :: WARN ObjectStore: Failed to get database default, returning NoSuchObjectException
spark-sql> show databases;
default
test
Time taken: 3.93 seconds, Fetched  row(s)
spark-sql> show tables;
default copyemp false
default demo    false
default dept    false
default dual    false
default emp false
default empbak  false
default employees   false
default mytb    false
default users   false
Time taken: 0.145 seconds, Fetched  row(s)
spark-sql> select * from emp;
    CLARK   MANAGER     --  2450.0  0.0
    KING    PRESIDENT      --  5000.0  0.0
    MILLER  CLERK       --  1300.0  0.0
    SMITH   CLERK       --  800.0   0.0
    JONES   MANAGER     --  2975.0  0.0
    FORD    ANALYST     --  3000.0  0.0
    ALLEN   SALESMAN        --  1600.0  300.0
    WARD    SALESMAN        --  1250.0  500.0
    MARTIN  SALESMAN        --  1250.0  1400.0
    BLAKE   MANAGER     --  2850.0  0.0
    TURNER  SALESMAN        --  1500.0  0.0
    JAMES   CLERK       --  950.0   0.0
    HADRON  NULL    NULL    --  6666.0  NULL    NULL
Time taken: 3.266 seconds, Fetched  row(s)
spark-sql>