Cassandra - CQL User Defined Datatypes

CQL provides the facipty of creating and using user-defined data types. You can create a data type to handle multiple fields. This chapter explains how to create, alter, and delete a user-defined data type.

Creating a User-defined Data Type

The command CREATE TYPE is used to create a user-defined data type. Its syntax is as follows −

CREATE TYPE <keyspace name>. <data typename>
( variable1, variable2).

Example

Given below is an example for creating a user-defined data type. In this example, we are creating a card_details data type containing the following details.

cqlsh:tutorialspoint> CREATE TYPE card_details (
   ... num int,
   ... pin int,
   ... name text,
   ... cvv int,
   ... phone set<int>
... );

Note − The name used for user-defined data type should not coincide with reserved type names.

Verification

Use the DESCRIBE command to verify whether the type created has been created or not.

CREATE TYPE tutorialspoint.card_details (
   num int,
   pin int,
   name text,
   cvv int,
   phone set<int>
   );

Altering a User-defined Data Type

ALTER TYPE − command is used to alter an existing data type. Using ALTER, you can add a new field or rename an existing field.

Adding a Field to a Type

Use the following syntax to add a new field to an existing user-defined data type.

ALTER TYPE typename
ADD field_name field_type; 

The following code adds a new field to the Card_details data type. Here we are adding a new field called email.

cqlsh:tutorialspoint> ALTER TYPE card_details ADD email text;

Verification

Use the DESCRIBE command to verify whether the new field is added or not.

cqlsh:tutorialspoint> describe type card_details;
CREATE TYPE tutorialspoint.card_details (
   num int,
   pin int,
   name text,
   cvv int,
   phone set<int>,
   );

Renaming a Field in a Type

Use the following syntax to rename an existing user-defined data type.

ALTER TYPE typename
RENAME existing_name TO new_name;

The following code changes the name of the field in a type. Here we are renaming the field email to mail.

cqlsh:tutorialspoint> ALTER TYPE card_details RENAME email TO mail;

Verification

Use the DESCRIBE command to verify whether the type name changed or not.

cqlsh:tutorialspoint> describe type card_details;
CREATE TYPE tutorialspoint.card_details (
   num int,
   pin int,
   name text,
   cvv int,
   phone set<int>,
   mail text
   );

Deleting a User-defined Data Type

DROP TYPE is the command used to delete a user-defined data type. Given below is an example to delete a user-defined data type.

Example

Before deleting, verify the pst of all user-defined data types using DESCRIBE_TYPES command as shown below.

cqlsh:tutorialspoint> DESCRIBE TYPES;
card_details card

From the two types, delete the type named card as shown below.

cqlsh:tutorialspoint> drop type card;

Use the DESCRIBE command to verify whether the data type dropped or not.

cqlsh:tutorialspoint> describe types;

card_details