title: SQL Count unique objects defined by parameters
body: <p>I have a table with:</p>
  
  <pre><code>id | parameter
   1 | A
   1 | B
   2 | A
   3 | A
   3 | B
  </code></pre>
  
  <p>That represent objects defined with the values as:</p>
  
  <pre><code> 1 -&gt; A,B
   2 -&gt; A
   3 -&gt; A,B
  </code></pre>
  
  <p>I want to count the number of objects with different parameters using a SQL query, so in this case it would be 2 unique objects as 1 and 3 have the same parameters.</p>
  
  <p>There is no constraint on the number of parameters, there can be 0, or any other number.</p>
  
  <p>The database is a Microsoft SQL Server 2000. But I do not mind knowing the solution for other databases.</p>