title: T-SQL First_Value() - How can it return more than a single value?
body: <p>I have the following query:</p>
  
  <pre><code>Select PH.SubId
  From dbo.PanelHistory PH
  Where 
      PH.Scribe2Time &lt;&gt; (Select FIRST_VALUE(ReadTimeLocal) OVER (Order By ReadTimeLocal) From dbo.PanelWorkflow Where ProcessNumber = 2690 And dbo.PanelWorkflow.SubId = PH.SubId)
  </code></pre>
  
  <p>I'm getting an error (512) that says:  <code>Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, &lt;, &lt;= , &gt;, &gt;= or when the subquery is used as an expression.</code></p>
  
  <p>How can the subquery return more than a single value? There can only be one first value. I must be overlooking something with this query.</p>
  
  <p>By the way, I realize I could easily use Min() instead of First_Value, but I wanted to experiment with some of these Windowing functions.</p>