Cassandra Storage List Array

The demo is as follows:

CREATE TABLEUsers3 (user_id text PRIMARY KEY, first_nametext, Last_Nametext, emails list<text>);INSERT  intoUSERS3 (user_id, first_name, last_name, emails)VALUES('Frodo','Frodo','Baggins',[' [email protected] ', ' [email protected] ']);UPDATEUsers3SETEmails=Emails+ [' [email protected] '] WHERE user_id = 'Frodo'; SELECT user_id, emails fromUsers3WHERE user_id = 'Frodo';

Collection type

A Collection column is declared using the collection type, followed by another type, such int as or text , in angle BRAC Kets. For example, you can create a table has a list of textual elements, a list of integers, or a list of some other element Types.

list<text>list<int>

Collection types cannot is nested, but frozen Collection types can be nested inside frozen or Non-frozen collections. For example, define a list within a list, provided the inner list is frozen:

list<frozen <list<int>>>

Indexes May is created on a collection column of any type.

Using frozen in a collection

A frozen value serializes multiple components to a single value. Non-frozen types allow updates to individual fields. Cassandra treats the value of a frozen type as a blob. The entire value must be overwritten.

collection_type<data_type, frozen<column_name>>

For example:

CREATE TABLE mykeyspace.users ( id uuid PRIMARY KEY, name frozen <fullname>, direct_reports set<frozen <fullname>>, // a collection set addresses map<text, frozen <address>> // a collection map score set<frozen <set<int>>> // a set with a nested frozen set);


list words for the following {} modified to [] can! 

Using the set type

A set stores a group of elements that is returned in sorted order when queried. A column of type set consists of unordered unique values. Using the Set data type, you can solve the multiple e-mail problem in an intuitive-to-a-to-does not require a read before Adding a new email address.

Procedure

2. define a set, emails, in the users table to accommodate multiple email address.

   create  TABLE users (user_id text  PRIMARY key, first_name text, last_name text, emails set<text>);    

4. insert data into the set, enclosing values In curly brackets. Set values must be unique.

   insert  Into users (user_id, first_name, last_name, emails) VALUES ( Span class= "hljs-string" > ' Frodo ',  ' Frodo ',  ' Baggins ', { ' [email protected] '});    

6. Add an element to a set using the UPDATE command and the addition (+) operator.

   Users  SET emails = emails + {' Frodo '; 

7. Retrieve email addresses for Frodo from the set.

   ' Frodo ';

   When you query a table containing a collection, Cassandra retrieves the collection with its entirety; Consequently, keep collections small enough to being manageable, or construct a data model to replace collections that can AC Commodate large amounts of data.

   Cassandra returns results in a order based on the type of the elements in the collection. For example, a set of the text elements is returned in alphabetical order. If you want elements of the collection returned on Insertion order, use a list.

   user_id | Emails---------+-------------------------------------------------------------------Frodo   | {"[Email protected]", "[email protected]", "[Email protected]"}

9. The Remove an element is from a set using the subtraction (-) operator.

   Users  SET emails = emails-{' Frodo '; 

10. Remove all elements from a set by using the UPDATE or DELETE statement.A set, list, or map needs to has at least one element; Otherwise, Cassandra cannot distinguish the set from a null value.

    ' Frodo ';      ' Frodo ';

    A query for the emails returns NULL.

    ' Frodo ';

    user_id | Emails---------+------------------------------------------------Frodo   | null
    
    
    Reference: http://docs.datastax.com/en/archived/cql/3.0/cql/cql_using/use_list_t.html

Cassandra Storage List Array