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Sunday, 1 January 2017

HBase Create Table Tutorial


Creating a Table using HBase Shell
     You can create a table using the create command, here you must specify the table name and the Column Family name. The syntax to create a table in HBase shell is shown below.
create ‘<table name>’,’<column family>’ 
Example
     Given below is a sample schema of a table named emp. It has two column families: “personal data” and “professional data”. You can create this table in HBase shell as shown below.
create 'emp', 'personal data', 'professional data'
     And it will give you the following output.
0 row(s) in 1.1300 seconds
=> Hbase::Table - emp
Creating a Table Using java API
     You can create a table in HBase using the createTable() method of HBaseAdmin class. This class belongs to the org.apache.hadoop.hbase.client package. Given below are the steps to create a table in HBase using java API.
Step 1: Instantiate HBaseAdmin
   HBaseAdmin class requires the Configuration object as a parameter, therefore initially instantiate the Configuration class and pass this instance to HBaseAdmin.
Configuration conf = HBaseConfiguration.create();
HBaseAdmin admin = new HBaseAdmin(conf);
Step 2: Create TableDescriptor
     HTableDescriptor is a class that belongs to the org.apache.hadoop.hbase class. This class is like a container of table names and column families.
HTableDescriptor table = new HTableDescriptor(toBytes("Table name"));
HColumnDescriptor family = new HColumnDescriptor(toBytes("column family"));
table.addFamily(family);
Step 3: Execute through Admin
     Using the createTable() method of HBaseAdmin class, you can execute the created table in Admin mode.
admin.createTable(table);
Example
package com.ashok.hbase;

import java.io.IOException;

import org.apache.hadoop.hbase.HBaseConfiguration;
import org.apache.hadoop.hbase.HColumnDescriptor;
import org.apache.hadoop.hbase.HTableDescriptor;
import org.apache.hadoop.hbase.client.HBaseAdmin;
import org.apache.hadoop.hbase.TableName;

import org.apache.hadoop.conf.Configuration;

public class CreateTable {
   public static void main(String[] args) throws IOException {

      // Instantiating configuration class
      Configuration conf = HBaseConfiguration.create();

      // Instantiating HbaseAdmin class
      HBaseAdmin admin = new HBaseAdmin(conf);

      // Instantiating table descriptor class
      HTableDescriptor td = new HTableDescriptor(TableName.valueOf("emp"));

      // Adding column families to table descriptor
      td.addFamily(new HColumnDescriptor("personal"));
      td.addFamily(new HColumnDescriptor("professional"));

      // Execute the table through admin
      admin.createTable(td);
      System.out.println(" Table created successfully");
   }
}

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