title: Concatenate Message In RAISERROR
body: <p>What's the proper syntax here?</p>
  
  <pre><code>If (@timestamp &lt; (Select PromoStartTimestamp From @promo))
      RAISERROR('Code not valid until ' + (Select PromoStartTimestamp From @promo)
                ,16
                ,1);
  </code></pre>
  
  <p>I've tried:</p>
  
  <pre><code>If (@timestamp &lt; (Select PromoStartTimestamp From @promo))
      RAISERROR(N'Code not valid until @starttimestamp'
                ,16
                ,1
                ,(Select PromoStartTimestamp From @promo));
  </code></pre>