Create a UDT

User-Defined Types (UDTs) can be used to store multiple data fields, each with a name and type, on one column. The fields in a UDT can be any valid data type, including collections and other UDTs.

To use a UDT, you must create the UDT itself, which is effectively a custom data type definition. After a UDT is created, you can use it to define a table column, like any other data type, with CREATE TABLE or ALTER TABLE. A UDT can be used in multiple tables, like any other data type.

UDTs are stored per keyspace. However, you can access a UDT defined on one keyspace from another keyspace by using the <keyspace_name>.<type_name> notation.

Use a CREATE TYPE statement to create a user-defined type named basic_info:

CREATE TYPE IF NOT EXISTS cycling.basic_info ( 
  birthday timestamp, 
  nationality text, 
  height text,
  weight text
);
DESCRIBE TYPE cycling.basic_info;

Results

Create a table for storing cyclist data in columns of type basic_info. Use the frozen keyword in the definition of the user-defined type column.

The frozen keyword is not required for UDTs that contain only non-collection fields.

When using the frozen keyword, you cannot update parts of a user-defined type value. The entire value must be overwritten. The database treats the value of a frozen, user-defined type like a blob.

CREATE TABLE IF NOT EXISTS cycling.cyclist_stats ( 
  id UUID PRIMARY KEY,
  lastname text,
  basics basic_info
);

A user-defined type can be nested in another column type. The example below nests a UDT in a frozen list named races.

CREATE TYPE IF NOT EXISTS cycling.race (
  race_title text,
  race_date timestamp,
  race_time text
);
DESCRIBE TYPE cycling.race;

Results

CREATE TABLE IF NOT EXISTS cycling.cyclist_races (
  id UUID PRIMARY KEY,
  lastname text,
  firstname text,
  races list<FROZEN <race>>
);

Results

Create a UDT

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