title: Query in order to select only the first record
body: <p>In SQL Server, how can I select only the first record from a table containing multiple records for each <code>CustomerID</code>?</p>
  
  <p>Sample data:<br/></p>
  
  <pre><code>CustomerID | Name     | Email              | Phone
  123        | Emiliano | emilaino@gmail.com | null
  123        | null     | emi@gmail.com      | 334455667
  123        | Emiliano | null               | 334455667
  110        | Pippo    | pippo@gmail.com    | 3232312
  110        | Pippo    | null               | 3232312
  110        | Pippo    | pippo@gmail.com    | null
  </code></pre>
  
  <p>Desired results:</p>
  
  <pre><code>123 | Emiliano | emilaino@gmail.com | null
  110 | Pippo    | pippo@gmail.com    | 3232312
  </code></pre>