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Collection data types in Apache Cassandra

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Release： 2023-08-25 22:37:09

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Apache Cassandra 中的集合数据类型

We will look at the Cassandra collection data type tutorial in our Cassandra journey. In this article, we will learn about Cassandra’s Collection data type. These data types have the same meaning as arrays and structures in C, C, etc.

Additionally, we will discuss Cassandra collection data types using lists, sets, and maps.

So, let’s start with the Cassandra collection data type.

Cassandra’s collection data type

In Cassandra, a collection data type is essentially a storage container for multiple values. Typically, Cassandra-CQL collection data types are defined by a single variable. The variable itself has a range of values.

Lists, sets and maps are several collection data types. Perform a wide range of operations on these Cassandra collection data types. These include create, insert, update, and verify operations.

a)Cassandra list

Values of this data type are saved in list form. The list contains multiple copies of a single value. For list data types, there is only one rule.

Elements cannot be modified sequentially. When a value is stored in a list, the element is assigned a specific index. These indexes can be used to obtain values.

i) Create table

In Cassandra, one can create a table with a list data type using the CREATE TABLE command. There may be many columns in the table. The syntax for creating a table is.

cqlsh:<keyspace>>CREATE TABLE <table name>(column1 PRIMARY KEY,column2 list <data type>,column3 list <data type>,.....);

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Construct a table containing the name, student number and branch of "college students".

cqlsh> USE keyspace1;
cqlsh:keyspace1> CREATE TABLE employee
                            ... (EN int,
                            ... NAME text,
                            ... EMAIL LIST,
                            ... PRIMARY KEY(EN),
                            ... );

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Output

one	Name	e-mail

ii) Insert

Users can use the INSERT INTO command to add components to the table. Each value enclosed in square brackets is separated by commas. The syntax is -

cqlsh:<keyspace>> INSERT INTO <table name>(column1, column2, column3,....) VALUES('R1value1',['R1value1','R1value2','R1value3'...]['R1value11','R1value12','R1value13'...]...);

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Example

cqlsh:keyspace1> INSERT INTO college student (EN, NAME, EMAIL)
                        ... VALUES(001,'hardik',{'hardi@gmail.com'});
cqlsh:keyspace1> INSERT INTO college student (EN, NAME, EMAIL)
                        ... VALUES(002,'Ajites',{'ajit@mail.com'});
cqlsh:keyspace1> INSERT INTO college student (EN, NAME, EMAIL)
                        ... VALUES(003,'Pushpa',{'tears@mail.com'});

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Output

one	Name	e-mail
001	Hardik	hardi@gmail.com
002	Ajites	ajit@mail.com
003	Pushpa	tears@mail.com

iii) Update

Cassandra's UPDATE command is used to update the values of certain table columns. The updated syntax is as follows.

cqlsh:<keyspace> UPDATE<table name>
SET <column2>=<column2>+['value']
where <column1>='some value';

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Example

cqlsh:keyspace2>UPDATE college student
SET EMAIL=EMAIL+['hardikgupta.1@gmail.com']
where EN=001;

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Output

one	Name	e-mail
001	Hardik	hardikgupta.1@gmail.com
002	Ajites	ajit@mail.com
003	Pushpa	tears@mail.com

b) Cassandra Set

Users can use the SET Cassandra collection data type to store collections of elements. After execution, the components of the collection are returned in sorted order.

I. Create table

Users can use the construct command with the following syntax to create the table containing the set.

cqlsh:<keyspace> CREATE TABLE<table name> (column1 PRIMARY KEY, column2 set <data type>, column3 set <data type>.....);

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Example

Construct a table containing the name, student number and branch of "college students".

cqlsh> USE keyspace2;
cqlsh:keyspace2> CREATE TABLE employee
                            ... (EN int,
                            ... NAME text,
                            ... EMAIL LIST<text>,
                            ... PRIMARY KEY(EN),
                            ... );

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Output

one	Name	e-mail

ii.Cassandra insertion

INSERT INTO command is used with the following syntax to insert values into a collection.

cqlsh:<keyspace>> INSERT INTO <table name>(column1, column2, column3...) VALUES('R1value',{'R1value1', 'R1value2',..},{ 'R1value11', 'R1value12',..}....);

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Example

>
cqlsh:keyspace2> INSERT INTO college student (EN, NAME, EMAIL)
                        ... VALUES(001,'hardik',{'hardi@gmail.com'});
cqlsh:keyspace2> INSERT INTO college student (EN, NAME, EMAIL)
                        ... VALUES(002,'Ajites',{'ajit@mail.com'});
cqlsh:keyspace2> INSERT INTO college student (EN, NAME, EMAIL)
                        ... VALUES(003,'Pushpa',{'tears@mail.com'});

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Output

one	Name	e-mail
001	Hardik	hardi@gmail.com
002	Ajites	ajit@mail.com
003	Pushpa	tears@mail.com

iii. Cassandra Update

Users can use this syntax to update content in the collection.

cqlsh:<keyspace>>UPDATE <table name>
SET <column2>=<column2>+['value']
where <column1>='some value';

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Example

cqlsh:keyspace2>UPDATE college student
SET EMAIL=EMAIL+['hardikgupta.1@gmail.com']
where EN=001;

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Output

one	Name	e-mail
001	Hardik	hardikgupta.1@gmail.com
002	Ajites	ajit@mail.com
003	Pushpa	tears@mail.com

c)Cassandra 地图

一对键值项存储在映射（Cassandra 集合数据类型）中。

我。创建表

用户可以使用以下语法的“构造”命令来创建带有地图的表。

cqlsh:<keyspace> CREATE TABLE<table name> (column1 PRIMARY KEY, column2 map <type, data type>, column3 map <type, data type>.....);

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构建一个表，其中包含“大学生”的名称、学号和分支。

cqlsh> USE keyspace3;
cqlsh:keyspace3> CREATE TABLE employee
                            ... (EN int,
                            ... NAME text,
                            ... EMAIL LIST,
                            ... PRIMARY KEY(EN),
                            ... );

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输出

一个	姓名	电子邮件

ii.插入

INSERT INTO 命令与以下语法一起使用，将值插入到映射中。

cqlsh:<keyspace>> INSERT INTO <table name>(column1, column2, column3...) VALUES('R1value',{'R1value1':'R1value1' ,R1value2:'R1value01',..},{ 'R1value11':'R1value011','R1value12':'R1value012',..}....);

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示例

cqlsh:keyspace3> INSERT INTO college student (EN, NAME, EMAIL)
                        ... VALUES(001,'hardik',{'hardi@gmail.com'});
cqlsh:keyspace3> INSERT INTO college student (EN, NAME, EMAIL)
                        ... VALUES(002,'Ajites',{'ajit@mail.com'});
cqlsh:keyspace3> INSERT INTO college student (EN, NAME, EMAIL)
                        ... VALUES(003,'Pushpa',{'tears@mail.com'});

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输出

一个	姓名	电子邮件
001	哈迪克	hardi@gmail.com
002	阿吉特斯	ajit@mail.com
003	普什帕	tears@mail.com

iii.更新

使用此技术，用户可以修改集合的内容。

cqlsh:<keyspace>>UPDATE <table name>
SET <column2>=<column2>+['value1':'value2']
where <column1>='some value';

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示例

cqlsh:keyspace3>UPDATE college student
SET EMAIL=EMAIL+['hardikgupta.1@gmail.com']
where EN=001;

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输出

一个	姓名	电子邮件
001	哈迪克	hardikgupta.1@gmail.com
002	阿吉特斯	ajit@mail.com
003	普什帕	tears@mail.com

结论

这是 Apache Cassandra 中的三种集合数据类型。通过 Cassandra 集合可以轻松进行任务管理。集合允许存储大量项目。

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