cassandra/doc/source/data_modeling/data_modeling_schema.rst

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.. highlight:: cql

Defining Database Schema
========================

Once you have finished evaluating and refining the physical model, you’re
ready to implement the schema in CQL. Here is the schema for the
``hotel`` keyspace, using CQL’s comment feature to document the query
pattern supported by each table::

    CREATE KEYSPACE hotel WITH replication =
      {‘class’: ‘SimpleStrategy’, ‘replication_factor’ : 3};

    CREATE TYPE hotel.address (
      street text,
      city text,
      state_or_province text,
      postal_code text,
      country text );

    CREATE TABLE hotel.hotels_by_poi (
      poi_name text,
      hotel_id text,
      name text,
      phone text,
      address frozen<address>,
      PRIMARY KEY ((poi_name), hotel_id) )
      WITH comment = ‘Q1. Find hotels near given poi’
      AND CLUSTERING ORDER BY (hotel_id ASC) ;

    CREATE TABLE hotel.hotels (
      id text PRIMARY KEY,
      name text,
      phone text,
      address frozen<address>,
      pois set )
      WITH comment = ‘Q2. Find information about a hotel’;

    CREATE TABLE hotel.pois_by_hotel (
      poi_name text,
      hotel_id text,
      description text,
      PRIMARY KEY ((hotel_id), poi_name) )
      WITH comment = Q3. Find pois near a hotel’;

    CREATE TABLE hotel.available_rooms_by_hotel_date (
      hotel_id text,
      date date,
      room_number smallint,
      is_available boolean,
      PRIMARY KEY ((hotel_id), date, room_number) )
      WITH comment = ‘Q4. Find available rooms by hotel date’;

    CREATE TABLE hotel.amenities_by_room (
      hotel_id text,
      room_number smallint,
      amenity_name text,
      description text,
      PRIMARY KEY ((hotel_id, room_number), amenity_name) )
      WITH comment = ‘Q5. Find amenities for a room’;


Notice that the elements of the partition key are surrounded
with parentheses, even though the partition key consists
of the single column ``poi_name``. This is a best practice that makes
the selection of partition key more explicit to others reading your CQL.

Similarly, here is the schema for the ``reservation`` keyspace::

    CREATE KEYSPACE reservation WITH replication = {‘class’:
      ‘SimpleStrategy’, ‘replication_factor’ : 3};

    CREATE TYPE reservation.address (
      street text,
      city text,
      state_or_province text,
      postal_code text,
      country text );

    CREATE TABLE reservation.reservations_by_confirmation (
      confirm_number text,
      hotel_id text,
      start_date date,
      end_date date,
      room_number smallint,
      guest_id uuid,
      PRIMARY KEY (confirm_number) )
      WITH comment = ‘Q6. Find reservations by confirmation number’;

    CREATE TABLE reservation.reservations_by_hotel_date (
      hotel_id text,
      start_date date,
      end_date date,
      room_number smallint,
      confirm_number text,
      guest_id uuid,
      PRIMARY KEY ((hotel_id, start_date), room_number) )
      WITH comment = ‘Q7. Find reservations by hotel and date’;

    CREATE TABLE reservation.reservations_by_guest (
      guest_last_name text,
      hotel_id text,
      start_date date,
      end_date date,
      room_number smallint,
      confirm_number text,
      guest_id uuid,
      PRIMARY KEY ((guest_last_name), hotel_id) )
      WITH comment = ‘Q8. Find reservations by guest name’;

    CREATE TABLE reservation.guests (
      guest_id uuid PRIMARY KEY,
      first_name text,
      last_name text,
      title text,
      emails set,
      phone_numbers list,
      addresses map<text,
      frozen<address>,
      confirm_number text )
      WITH comment = ‘Q9. Find guest by ID’;

You now have a complete Cassandra schema for storing data for a hotel
application.

*Material adapted from Cassandra, The Definitive Guide. Published by
O'Reilly Media, Inc. Copyright © 2020 Jeff Carpenter, Eben Hewitt.
All rights reserved. Used with permission.*