Cassandra - คอลเลกชัน CQL

CQL จัดเตรียมสิ่งอำนวยความสะดวกในการใช้ประเภทข้อมูล Collection เมื่อใช้ประเภทคอลเล็กชันเหล่านี้คุณสามารถจัดเก็บหลายค่าในตัวแปรเดียวได้ บทนี้จะอธิบายถึงวิธีการใช้ Collections ใน Cassandra

รายการ

รายการใช้ในกรณีที่

• ลำดับขององค์ประกอบจะต้องได้รับการบำรุงรักษาและ
• ค่าจะถูกจัดเก็บหลายครั้ง

คุณสามารถรับค่าของชนิดข้อมูลรายการโดยใช้ดัชนีขององค์ประกอบในรายการ

การสร้างตารางด้วยรายการ

Given below is an example to create a sample table with two columns, name and email. To store multiple emails, we are using list.

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

Inserting Data into a List

While inserting data into the elements in a list, enter all the values separated by comma within square braces [ ] as shown below.

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

Updating a List

Given below is an example to update the list data type in a table called data. Here we are adding another email to the list.

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

Verification

If you verify the table using SELECT statement, you will get the following result −

cqlsh:tutorialspoint> SELECT * FROM data;

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

(1 rows)

SET

Set is a data type that is used to store a group of elements. The elements of a set will be returned in a sorted order.

Creating a Table with Set

The following example creates a sample table with two columns, name and phone. For storing multiple phone numbers, we are using set.

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

Inserting Data into a Set

While inserting data into the elements in a set, enter all the values separated by comma within curly braces { } as shown below.

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

Updating a Set

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

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

Verification

If you verify the table using SELECT statement, you will get the following result −

cqlsh:tutorialspoint> SELECT * FROM data2;

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

(1 rows)

MAP

Map is a data type that is used to store a key-value pair of elements.

Creating a Table with Map

The following example shows how to create a sample table with two columns, name and address. For storing multiple address values, we are using map.

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

Inserting Data into a Map

While inserting data into the elements in a map, enter all the key : value pairs separated by comma within curly braces { } as shown below.

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

Updating a Set

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

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

Verification

If you verify the table using SELECT statement, you will get the following result −

cqlsh:tutorialspoint> select * from data3;

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

(1 rows)