Database

The database in Hive describes a collection of tables that are used for a similar purpose or belong to the same groups. If the database is not specified, the default database is used and uses /user/hive/warehouse in HDFS as its root directory. This path is configurable by the hive.metastore.warehouse.dir property in hive-site.xml. Whenever a new database is created, Hive creates a new directory for each database under /user/hive/warehouse. For example, the myhivebook database is located at /user/hive/datawarehouse/myhivebook.db. In addition, DATABASE has a name alias, SCHEMA, meaning they are the same thing in HQL. The following is the major DDL for databases operations:

1. Create the database/schema if it doesn't exist:

      > CREATE DATABASE myhivebook;
      > CREATE SCHEMA IF NOT EXISTS myhivebook; 

2. Create the database with the location, comments, and metadata information:

      > CREATE DATABASE IF NOT EXISTS myhivebook
      > COMMENT 'hive database demo'
      >...