【Hive】Hive编程指南（Part 2），

第五章 HiveQL：数据操作

向管理表中装载数据

LOAD DATA LOCAL INPATH '${env:HOME}/california-employees'
OVERWRITE INTO TABLE employees
PARTITION (country = 'US', state = 'CA');

通过查询语句向表中插入数据

1. 按一种方式进行划分

INSERT OVERWRITE TABLE employees
PARTITION (country = 'US', state = 'OR')
SELECT * FROM staged_employees se
WHERE se.cnty = 'US' AND se.st = 'OR';

2. 按多种方式进行划分

FROM staged_employees se
INSERT OVERWRITE TABLE employees
    PARTITION (country = 'US', state = 'OR')
    SELECT * WHERE se.cnty = 'US' AND se.st = 'OR'; 
INSERT OVERWRITE TABLE employees
    PARTITION (country = 'US', state = 'CA')
    SELECT * WHERE se.cnty = 'US' AND se.st = 'CA';
INSERT OVERWRITE TABLE employees
    PARTITION (country = 'US', state = 'IL')
    SELECT * WHERE se.cnty = 'US' AND se.st = 'IL';

3. 动态分区插入

INSERT OVERWRITE TABLE employees
PARTITION (country, state)
SELECT ..., se.cnty, e.st
FROM staged_employees se;

Hive根据SELECT语句中最后2列来确定分区字段country和state的值。

单个查询语句中创建表并加载数据

CREATE TABLE ca_employees
AS SELECT name, salary, address
FROM employess
WHERE state = 'CA';

这个功能不能用于外部表。

导出数据

如果数据文件恰好是用户需要的格式，那么只需要简单地拷贝文件夹或文件就可以了。

hadoop fs -cp source_path target_path

否则，使用INSERT ... DIRECTORY ...，例如：

INSERT OVERWRITE LOCAL DIRECTORY '/tmp/ca_employees'
SELECT name, salary, address
FROM employees
WHERE se.state = 'CA';