hive与dolphin笔记

一、hive相关

1. 如何增加列

增加多列：

ALTER TABLE user_profile
ADD COLUMNS(
	return_distance string, 
	return_duration string
);

增加多列并添加注释：

ALTER TABLE example_table 
ADD COLUMNS (
    salary DOUBLE COMMENT 'The salary of the employee',
    department STRING COMMENT 'The department where the employee works'
);

2. 如何添加或修改列的注释

ALTER TABLE user_profile change COLUMN distance 
distance string COMMENT '距离';

ALTER TABLE user_profile change COLUMN duration 
duration string COMMENT '时长';

3. 如何查看表的具体列的数据类型

DESCRIBE your_table_name

4. 如何drop一个表

drop table your_table_name

5. 如何设置前置项

set mapreduce.job.queuename=your_queue_name;

set hive.exec.parallel=true;
set hive.exec.parallel.thread.number=10;
set mapred.job.name=your_job_name;
set ma