Cassandra CQL collection

CQL provides the ibility to use TheCollection data type. U sing these collection types, you can store multiple values in a single variable. This chapter describes how to use Colleges in Cassandra.

List

List is used in the following cases

• The order of the elements is maintained, and
• The value will be stored more than once.

You can use the index of elements in the list to get the value of the list data type.

Create a table with List

Here's an example of creating a sample table with two columns (name and e-mail). To store multiple e-mail messages, we use lists.

cqlsh:tutorialspoint> CREATE TABLE data(name text PRIMARY KEY, email list<text>);

Insert data into the list

When you insert data into an element in the list, enter all the values separated by commas in square brackets like the following.

cqlsh:tutorialspoint> INSERT INTO data(name, email) VALUES ('ramu',
['[email protected]','[email protected]'])

Update the list

Here's an example of updating the list data type in a table called data. Here, we're adding another email to the list.

cqlsh:tutorialspoint> UPDATE data
... SET email = email +['[email protected]']
... where name = 'ramu';

Verify

If you validate the table with the SELECT statement, you get the following results:

cqlsh:tutorialspoint> SELECT * FROM data;

 name | email
------+--------------------------------------------------------------
 ramu | ['[email protected]', '[email protected]', '[email protected]']

(1 rows)

Set

Set is the type of data used to store a set of elements. The elements of the collection are returned in sort order.

Create a table with Set

The following example creates a sample table with two columns (name and phone). For storing multiple phone numbers, we use collections.

cqlsh:tutorialspoint> CREATE TABLE data2 (name text PRIMARY KEY, phone set<varint>);

Insert data into the collection

When you insert data into an element in a collection, enter all the values separated by commas in parentheses, as shown below.

cqlsh:tutorialspoint> INSERT INTO data2(name, phone)VALUES ('rahman',    {9848022338,9848022339});

Update the collection

The following code shows how to update a collection in a table named data2. Here, we are adding another phone number.

cqlsh:tutorialspoint> UPDATE data2
   ... SET phone = phone + {9848022330}
   ... where name = 'rahman';

Verify

If you validate the table with the SELECT statement, you get the following results:

cqlsh:tutorialspoint> SELECT * FROM data2;

   name | phone
--------+--------------------------------------
 rahman | {9848022330, 9848022338, 9848022339}

(1 rows)

Map

A map is the type of data that is used to store key-value pairs of elements.

Use Map to create a table

The following example shows how to create a sample table with two columns (name and address). In order to store multiple address values, we use map.

cqlsh:tutorialspoint> CREATE TABLE data3 (name text PRIMARY KEY, address
map<timestamp, text>);

Insert data into the map

When you insert data into elements in the map, enter all the keys: value pairs, separated by commas between commas, as shown below.

cqlsh:tutorialspoint> INSERT INTO data3 (name, address)
   VALUES ('robin', {'home' : 'hyderabad' , 'office' : 'Delhi' } );

Update the collection

The following code shows how to update the map data type in a table named data3. Here, we change the value of the key office, that is, we change the office address of a person named Robin.

cqlsh:tutorialspoint> UPDATE data3
   ... SET address = address+{'office':'mumbai'}
   ... WHERE name = 'robin';

Verify

If you validate the table with the SELECT statement, you get the following results:

cqlsh:tutorialspoint> select * from data3;

  name | address
-------+-------------------------------------------
 robin | {'home': 'hyderabad', 'office': 'mumbai'}

(1 rows)