Basic Hbase commands
Hbase commands:

HBase has  a shell through which we can communicate with Hbase. The operations which can be performed on Hbase are given below.

DDL Operations:

1) Create:

            A table is created by giving table name and column family names.. The syntax is as below:
Text Box: create ‘<table name>’,’<column family>’

2) List:

Text Box: list

            This command returns the list of all tables which are available.

3) Disable:

            To delete a table or change any table settings, we need to disable the table first.
Text Box: disable ‘<table name>’

Below command disables the table.

            After disabling the table, we can verify it through the ‘scan’ command which will throw an error.

Text Box: hbase(main):001:0> scan ‘<table name>’
ERROR: ‘<table name>’ does not exist

4) disable_all:

            Multiple tables can be disabled at a time using disable_all command.
Text Box: disable_all ‘emp.*’

For example: TTo disable all the tables which starts with word ‘emp’, we can use as below:

5) Is_disabled:

            Below command is to check whether a table is in disabled state or not by using ‘is_disabled’ command.

Syntax is as below:
Text Box: is_disabled ‘<table name>’

6) Enable:

Text Box: enable ‘<table name>’

           we can enable a disabled table using the above command.

7) is_enabled:

            We can verify if the table is in enabled stated or not using the below command

Text Box: is_enabled ‘<table name>’

8) Describe:
Text Box: describe ‘<table name>’

            This command shows the description of the table. Below is the syntax.

9) Alter:

            To modify the existing table alter command is used. Using Alter command, we can perform below operations:
§  Add new column family
§  Delete existing column family.
§  Table can be set to  Read only mode.
§  maximum no.of cells for a column family can be set.
§ compression technique to be enabled for the table.

Text Box: alter ‘<table name>’, NAME => ‘< column family name >’

a) Syntax to add new column family to an existing table is shown:

b) Syntax to delete existing column family from the table is shown:

Text Box: alter ‘<table name>’, delete => ‘< column family name >’

c) Syntax to set table to read-only mode:

Text Box: alter ‘<table name>’, READONLY

d) Syntax to set maximum versions to a column family is shown below:

Text Box: alter ‘<table name>’, NAME => ‘< column family name >’ , VERSIONS => 5

e) Syntax to enable compression to the table:

Text Box: alter ‘<table name>’, NAME => ‘< column family name >’ , COMPRESSION => ‘snappy’

10) Exists:
Text Box: exists ‘<table name>’

            To verify whether a table is exists or not using the below command.

11) Drop:
            A table is  dropped by using the below command. However, to drop any table, first we need to disable that table and then drop it.

12) Drop_all:
            Multiple tables can be droped by using ‘drop_all’ command. Below is the syntax:
Ex: To drop all the tables which starts with word ‘emp’, then use as below.
Text Box: disable_all ‘emp.*’

First we need to disable these tables.

Text Box: drop_all ‘emp.*’

DML Operations:
            Below are the DML operations that can be performed in Hbase.
1) Put:
Text Box: put ‘<table name>’ , ‘<row>’, ‘<column family:column name>’, ‘<value>’

            Put command is used to insert data in the table. Below is the syntax for the same:

Text Box: put ‘student’, ‘1’, ‘dept:name’, ‘chemistry’

2) Update:
Text Box: put ‘<table name>’ , ‘<rowid>’, ‘<column family:column name>’, ‘<new value>’

            Using update command, we could update existing cell value to a new value. Below is the syntax:

If below command is executed, depart name of the student will get changed to physics from chemistry
Text Box: put ‘student’, ‘1’, ‘dept:name’, ‘Physics’

3) Get:
Text Box: get ‘<table name>’ , ‘<rowid>’

            Using  the Get command, we can read the data from Hbase.
Below is the syntax.

Reading a specific column:
below is the syntax to read a specific cell from the column family, .
Text Box: get ‘<table name>’ , ‘<rowid>’, {COLUMN => ‘<column family:column name>’}

4) Delete:
Text Box: delete ‘<table name>’ , ‘<rowid>’, ‘<column name>’, ‘<timestamp>’

            Using delete command, we can delete specific cell from the table. Below is the syntax:

5) Delete all:
Text Box: delete_all ‘<table name>’ , ‘<rowid>’

            Using Delete all command, all the cells in a particular row can be deleted.

6) Scan:
Text Box: scan ‘<table name>’

            Using Scan command, we can view data in the table.

7) Count:
Text Box: count ‘<table name>’

            Using count command, we can count no.of rows in a table.

8) Truncate:
            Using truncate command, we could truncate the table. It disables, drops and re-creates an empty table.
Text Box: truncate ‘<table name>’