how to form composite unique key in dynamo db
<p>I have a table in dynamo DB with the fields A, B, C, D and E.
The primary key is A(partition key) and B(sort key).</p>

<p>I want to have another unique constraint for C and D together as a composite unique key. In mysql I would do something like this</p>

<pre><code>ALTER TABLE YourTable
 add CONSTRAINT YourTable_unique UNIQUE (C, D);
</code></pre>

<p>I want to do something similar in dynamo DB so that when i create a new entry with an already matching composite unique key(C and D), it does not allow me to create that entry.</p>