hive

Hive

The Apache Hive data warehouse software facilitates reading, writing, and managing large datasets residing in distributed storage using SQL. Structure can be projected onto data already in storage. A command line tool and JDBC driver are provided to connect users to Hive.

进入hive

hive
hive --service cli
hive -S #静默模式 不打印输出信息

hive命令

show databases;
use <dbname>; -- 连接数据库
show tables;
show functions; --显示内置函数

desc <tbl>;     -- 显示表结构
dfs -ls <dir>;   -- 在hive里显示hdfs的目录

create table person 
(id int,
name string,
married boolean,
salary double);

desc  person;
------------------------------
create table student 
( id int,
  name string,
  grade array<float>);

------------------------------
create table student
( id int,
  name string,
  grade map<string, float>);
------------------------------
create table student
( id int,
  info struct<name: string, age:int, gender: string>
);

hive执行shell命令

!pwd;
!ls;
! cat /proc/cpuinfo;

HQL 查询

select * from tbl; --不会转换为 MapReduce
select title from tbl; -- 转换为 MapReduce