hive之managed table创建

Welcome to the world of Hive-0.10.0, now we will use Managed Tables:

1. hive> create database if not exists dataprocess

           >  comment 'analyze cluster data'

           >  location '/home/landen/UntarFile/hive-0.10.0/user/hive/warehouse';

Notice: you can optionally specify a location for the table data(as opposed to metadata, which the metastore will always hold). By default, hive always creates the table's directory under the directory for the enclosing database. The exception is the default database. It doesn't have a directory under /user/hive/warehouse(unless explicitly overridden).

2. hive> describe database financials;

    financials   analyze cluster data 

    hdfs://localhost:9000/home/landen/UntarFile/hive-0.10.0/user/hive/warehouse/dataprocess.db

3. hive> use dataprocess;

    and you can set a property to print the current database as part of the prompt

    hive> set hive.cli.print.current.db=true;

   hive(dataprocess)> ......

4. hive> drop database if exists dataprocess;

    Notice: By default, Hive won't permit you to drop a database if it contains tables. You can either drop the tables first or append the 'CASCADE' keyword to the command.

    hive> drop database if exists dataprocess CASCADE;

Using the 'RESTRICT' keyword instead of CASCADE is equivalent to the default behavior, where a database is dropped, it's directory is also deleted.

5. hive> alter database dataprocess

           > set dbproperties('edited-by' = 'kevin');

Now let's create a emplyees in the database of human_resources:

6. hive> use human_resources;

    hive> set hive.cli.print.current.db=true;

    hive(human_resources)> create table if not exists employees(

                                           > name string comment 'employee name',

                                           > number string comment 'employee work number')

                                           > comment 'describe the employee table'

                                           > tblproperies('creator'='landen', 'created_at'='2013-03-25 20:02');

    hive(human_resources)>  show tblproperties employees;

Notice: you can also copy the schema(but the data) of an existing table:

7. hive> create table if not exists mydb.employees

           >  like employees;

8. hive> use default;

    hive> show tables in mydb;

employees

9. hive> use mydb;

    hive> show tables 'empl.*';

Notice: if you only want to see the schema for a particular column, append the column to the table name,such as

10.  hive> describe mydb.employees.name

name string Employee name

      Now the tables we have created so far are called managed tables or sometimes called internal tables, because Hive controls the lifecycle of their data(more or less). As we've seen, Hive stores the data for these tables in a subdirectory under the directory defined by hive.metastore.warehouse.dir by default.

      However, managed tables are less convinent for sharing with other tools. For example, suppose we have data that is created and used primarily by Pig or other tools, but we want to run some quries against it, but not give Hive ownership of the data. So we can define an external table that points to that data, but doesn't take ownership of it.