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  <div class="section" id="defining-database-schema">
<h1>Defining Database Schema<a class="headerlink" href="#defining-database-schema" title="Permalink to this headline">¶</a></h1>
<p>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
<code class="docutils literal notranslate"><span class="pre">hotel</span></code> keyspace, using CQL’s comment feature to document the query
pattern supported by each table:</p>
<div class="highlight-cql notranslate"><div class="highlight"><pre><span></span><span class="k">CREATE</span> <span class="k">KEYSPACE</span> <span class="n">hotel</span> <span class="k">WITH</span> <span class="n">replication</span> <span class="o">=</span>
  <span class="p">{</span><span class="err">‘</span><span class="n">class</span><span class="err">’</span><span class="p">:</span> <span class="err">‘</span><span class="n">SimpleStrategy</span><span class="err">’</span><span class="p">,</span> <span class="err">‘</span><span class="n">replication_factor</span><span class="err">’</span> <span class="p">:</span> <span class="mf">3</span><span class="p">};</span>

<span class="k">CREATE</span> <span class="k">TYPE</span> <span class="n">hotel</span><span class="mf">.</span><span class="n">address</span> <span class="p">(</span>
  <span class="n">street</span> <span class="nb">text</span><span class="p">,</span>
  <span class="n">city</span> <span class="nb">text</span><span class="p">,</span>
  <span class="n">state_or_province</span> <span class="nb">text</span><span class="p">,</span>
  <span class="n">postal_code</span> <span class="nb">text</span><span class="p">,</span>
  <span class="n">country</span> <span class="nb">text</span> <span class="p">);</span>

<span class="k">CREATE</span> <span class="k">TABLE</span> <span class="n">hotel</span><span class="mf">.</span><span class="n">hotels_by_poi</span> <span class="p">(</span>
  <span class="n">poi_name</span> <span class="nb">text</span><span class="p">,</span>
  <span class="n">hotel_id</span> <span class="nb">text</span><span class="p">,</span>
  <span class="n">name</span> <span class="nb">text</span><span class="p">,</span>
  <span class="n">phone</span> <span class="nb">text</span><span class="p">,</span>
  <span class="n">address</span> <span class="k">frozen</span><span class="o">&lt;</span><span class="n">address</span><span class="o">&gt;</span><span class="p">,</span>
  <span class="k">PRIMARY</span> <span class="k">KEY</span> <span class="p">((</span><span class="n">poi_name</span><span class="p">),</span> <span class="n">hotel_id</span><span class="p">)</span> <span class="p">)</span>
  <span class="k">WITH</span> <span class="n">comment</span> <span class="o">=</span> <span class="err">‘</span><span class="n">Q1</span><span class="mf">.</span> <span class="n">Find</span> <span class="n">hotels</span> <span class="n">near</span> <span class="n">given</span> <span class="n">poi</span><span class="err">’</span>
  <span class="k">AND</span> <span class="k">CLUSTERING</span> <span class="k">ORDER</span> <span class="k">BY</span> <span class="p">(</span><span class="n">hotel_id</span> <span class="k">ASC</span><span class="p">)</span> <span class="p">;</span>

<span class="k">CREATE</span> <span class="k">TABLE</span> <span class="n">hotel</span><span class="mf">.</span><span class="n">hotels</span> <span class="p">(</span>
  <span class="n">id</span> <span class="nb">text</span> <span class="k">PRIMARY</span> <span class="k">KEY</span><span class="p">,</span>
  <span class="n">name</span> <span class="nb">text</span><span class="p">,</span>
  <span class="n">phone</span> <span class="nb">text</span><span class="p">,</span>
  <span class="n">address</span> <span class="k">frozen</span><span class="o">&lt;</span><span class="n">address</span><span class="o">&gt;</span><span class="p">,</span>
  <span class="n">pois</span> <span class="k">set</span> <span class="p">)</span>
  <span class="k">WITH</span> <span class="n">comment</span> <span class="o">=</span> <span class="err">‘</span><span class="n">Q2</span><span class="mf">.</span> <span class="n">Find</span> <span class="n">information</span> <span class="n">about</span> <span class="n">a</span> <span class="n">hotel</span><span class="err">’</span><span class="p">;</span>

<span class="k">CREATE</span> <span class="k">TABLE</span> <span class="n">hotel</span><span class="mf">.</span><span class="n">pois_by_hotel</span> <span class="p">(</span>
  <span class="n">poi_name</span> <span class="nb">text</span><span class="p">,</span>
  <span class="n">hotel_id</span> <span class="nb">text</span><span class="p">,</span>
  <span class="n">description</span> <span class="nb">text</span><span class="p">,</span>
  <span class="k">PRIMARY</span> <span class="k">KEY</span> <span class="p">((</span><span class="n">hotel_id</span><span class="p">),</span> <span class="n">poi_name</span><span class="p">)</span> <span class="p">)</span>
  <span class="k">WITH</span> <span class="n">comment</span> <span class="o">=</span> <span class="n">Q3</span><span class="mf">.</span> <span class="n">Find</span> <span class="n">pois</span> <span class="n">near</span> <span class="n">a</span> <span class="n">hotel</span><span class="err">’</span><span class="p">;</span>

<span class="k">CREATE</span> <span class="k">TABLE</span> <span class="n">hotel</span><span class="mf">.</span><span class="n">available_rooms_by_hotel_date</span> <span class="p">(</span>
  <span class="n">hotel_id</span> <span class="nb">text</span><span class="p">,</span>
  <span class="nb">date</span> <span class="nb">date</span><span class="p">,</span>
  <span class="n">room_number</span> <span class="nb">smallint</span><span class="p">,</span>
  <span class="n">is_available</span> <span class="nb">boolean</span><span class="p">,</span>
  <span class="k">PRIMARY</span> <span class="k">KEY</span> <span class="p">((</span><span class="n">hotel_id</span><span class="p">),</span> <span class="nb">date</span><span class="p">,</span> <span class="n">room_number</span><span class="p">)</span> <span class="p">)</span>
  <span class="k">WITH</span> <span class="n">comment</span> <span class="o">=</span> <span class="err">‘</span><span class="n">Q4</span><span class="mf">.</span> <span class="n">Find</span> <span class="n">available</span> <span class="n">rooms</span> <span class="k">by</span> <span class="n">hotel</span> <span class="nb">date</span><span class="err">’</span><span class="p">;</span>

<span class="k">CREATE</span> <span class="k">TABLE</span> <span class="n">hotel</span><span class="mf">.</span><span class="n">amenities_by_room</span> <span class="p">(</span>
  <span class="n">hotel_id</span> <span class="nb">text</span><span class="p">,</span>
  <span class="n">room_number</span> <span class="nb">smallint</span><span class="p">,</span>
  <span class="n">amenity_name</span> <span class="nb">text</span><span class="p">,</span>
  <span class="n">description</span> <span class="nb">text</span><span class="p">,</span>
  <span class="k">PRIMARY</span> <span class="k">KEY</span> <span class="p">((</span><span class="n">hotel_id</span><span class="p">,</span> <span class="n">room_number</span><span class="p">),</span> <span class="n">amenity_name</span><span class="p">)</span> <span class="p">)</span>
  <span class="k">WITH</span> <span class="n">comment</span> <span class="o">=</span> <span class="err">‘</span><span class="n">Q5</span><span class="mf">.</span> <span class="n">Find</span> <span class="n">amenities</span> <span class="n">for</span> <span class="n">a</span> <span class="n">room</span><span class="err">’</span><span class="p">;</span>
</pre></div>
</div>
<p>Notice that the elements of the partition key are surrounded
with parentheses, even though the partition key consists
of the single column <code class="docutils literal notranslate"><span class="pre">poi_name</span></code>. This is a best practice that makes
the selection of partition key more explicit to others reading your CQL.</p>
<p>Similarly, here is the schema for the <code class="docutils literal notranslate"><span class="pre">reservation</span></code> keyspace:</p>
<div class="highlight-cql notranslate"><div class="highlight"><pre><span></span><span class="k">CREATE</span> <span class="k">KEYSPACE</span> <span class="n">reservation</span> <span class="k">WITH</span> <span class="n">replication</span> <span class="o">=</span> <span class="p">{</span><span class="err">‘</span><span class="n">class</span><span class="err">’</span><span class="p">:</span>
  <span class="err">‘</span><span class="n">SimpleStrategy</span><span class="err">’</span><span class="p">,</span> <span class="err">‘</span><span class="n">replication_factor</span><span class="err">’</span> <span class="p">:</span> <span class="mf">3</span><span class="p">};</span>

<span class="k">CREATE</span> <span class="k">TYPE</span> <span class="n">reservation</span><span class="mf">.</span><span class="n">address</span> <span class="p">(</span>
  <span class="n">street</span> <span class="nb">text</span><span class="p">,</span>
  <span class="n">city</span> <span class="nb">text</span><span class="p">,</span>
  <span class="n">state_or_province</span> <span class="nb">text</span><span class="p">,</span>
  <span class="n">postal_code</span> <span class="nb">text</span><span class="p">,</span>
  <span class="n">country</span> <span class="nb">text</span> <span class="p">);</span>

<span class="k">CREATE</span> <span class="k">TABLE</span> <span class="n">reservation</span><span class="mf">.</span><span class="n">reservations_by_confirmation</span> <span class="p">(</span>
  <span class="n">confirm_number</span> <span class="nb">text</span><span class="p">,</span>
  <span class="n">hotel_id</span> <span class="nb">text</span><span class="p">,</span>
  <span class="n">start_date</span> <span class="nb">date</span><span class="p">,</span>
  <span class="n">end_date</span> <span class="nb">date</span><span class="p">,</span>
  <span class="n">room_number</span> <span class="nb">smallint</span><span class="p">,</span>
  <span class="n">guest_id</span> <span class="nb">uuid</span><span class="p">,</span>
  <span class="k">PRIMARY</span> <span class="k">KEY</span> <span class="p">(</span><span class="n">confirm_number</span><span class="p">)</span> <span class="p">)</span>
  <span class="k">WITH</span> <span class="n">comment</span> <span class="o">=</span> <span class="err">‘</span><span class="n">Q6</span><span class="mf">.</span> <span class="n">Find</span> <span class="n">reservations</span> <span class="k">by</span> <span class="n">confirmation</span> <span class="n">number</span><span class="err">’</span><span class="p">;</span>

<span class="k">CREATE</span> <span class="k">TABLE</span> <span class="n">reservation</span><span class="mf">.</span><span class="n">reservations_by_hotel_date</span> <span class="p">(</span>
  <span class="n">hotel_id</span> <span class="nb">text</span><span class="p">,</span>
  <span class="n">start_date</span> <span class="nb">date</span><span class="p">,</span>
  <span class="n">end_date</span> <span class="nb">date</span><span class="p">,</span>
  <span class="n">room_number</span> <span class="nb">smallint</span><span class="p">,</span>
  <span class="n">confirm_number</span> <span class="nb">text</span><span class="p">,</span>
  <span class="n">guest_id</span> <span class="nb">uuid</span><span class="p">,</span>
  <span class="k">PRIMARY</span> <span class="k">KEY</span> <span class="p">((</span><span class="n">hotel_id</span><span class="p">,</span> <span class="n">start_date</span><span class="p">),</span> <span class="n">room_number</span><span class="p">)</span> <span class="p">)</span>
  <span class="k">WITH</span> <span class="n">comment</span> <span class="o">=</span> <span class="err">‘</span><span class="n">Q7</span><span class="mf">.</span> <span class="n">Find</span> <span class="n">reservations</span> <span class="k">by</span> <span class="n">hotel</span> <span class="k">and</span> <span class="nb">date</span><span class="err">’</span><span class="p">;</span>

<span class="k">CREATE</span> <span class="k">TABLE</span> <span class="n">reservation</span><span class="mf">.</span><span class="n">reservations_by_guest</span> <span class="p">(</span>
  <span class="n">guest_last_name</span> <span class="nb">text</span><span class="p">,</span>
  <span class="n">hotel_id</span> <span class="nb">text</span><span class="p">,</span>
  <span class="n">start_date</span> <span class="nb">date</span><span class="p">,</span>
  <span class="n">end_date</span> <span class="nb">date</span><span class="p">,</span>
  <span class="n">room_number</span> <span class="nb">smallint</span><span class="p">,</span>
  <span class="n">confirm_number</span> <span class="nb">text</span><span class="p">,</span>
  <span class="n">guest_id</span> <span class="nb">uuid</span><span class="p">,</span>
  <span class="k">PRIMARY</span> <span class="k">KEY</span> <span class="p">((</span><span class="n">guest_last_name</span><span class="p">),</span> <span class="n">hotel_id</span><span class="p">)</span> <span class="p">)</span>
  <span class="k">WITH</span> <span class="n">comment</span> <span class="o">=</span> <span class="err">‘</span><span class="n">Q8</span><span class="mf">.</span> <span class="n">Find</span> <span class="n">reservations</span> <span class="k">by</span> <span class="n">guest</span> <span class="n">name</span><span class="err">’</span><span class="p">;</span>

<span class="k">CREATE</span> <span class="k">TABLE</span> <span class="n">reservation</span><span class="mf">.</span><span class="n">guests</span> <span class="p">(</span>
  <span class="n">guest_id</span> <span class="nb">uuid</span> <span class="k">PRIMARY</span> <span class="k">KEY</span><span class="p">,</span>
  <span class="n">first_name</span> <span class="nb">text</span><span class="p">,</span>
  <span class="n">last_name</span> <span class="nb">text</span><span class="p">,</span>
  <span class="n">title</span> <span class="nb">text</span><span class="p">,</span>
  <span class="n">emails</span> <span class="k">set</span><span class="p">,</span>
  <span class="n">phone_numbers</span> <span class="k">list</span><span class="p">,</span>
  <span class="n">addresses</span> <span class="k">map</span><span class="o">&lt;</span><span class="nb">text</span><span class="p">,</span>
  <span class="k">frozen</span><span class="o">&lt;</span><span class="n">address</span><span class="o">&gt;</span><span class="p">,</span>
  <span class="n">confirm_number</span> <span class="nb">text</span> <span class="p">)</span>
  <span class="k">WITH</span> <span class="n">comment</span> <span class="o">=</span> <span class="err">‘</span><span class="n">Q9</span><span class="mf">.</span> <span class="n">Find</span> <span class="n">guest</span> <span class="k">by</span> <span class="n">ID</span><span class="err">’</span><span class="p">;</span>
</pre></div>
</div>
<p>You now have a complete Cassandra schema for storing data for a hotel
application.</p>
<p><em>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.</em></p>
</div>


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