title: Incorrect syntax due SQL query execution
body: <p>I'm trying to execute next query</p>
  
  <pre><code>DECLARE @ponumber varchar(50)
  DECLARE @gcas varchar(50)
  SET @ponumber = '3864_ab03963'
  SET @gcas = '81332119.'
  EXEC(N'SELECT * FROM tCleanOrderTracking_prod 
         WHERE [PO number] = ' + @ponumber + ' AND [GCAS] = ' + @gcas)
  </code></pre>
  
  <p>And I've got an error message </p>
  
  <pre><code>Msg 102, Level 15, State 1, Line 1
  Incorrect syntax near '_ab03963'.
  </code></pre>
  
  <p>What I'm doing wrong? </p>