title: tsql clash: Operand type clash: date is incompatible with tinyint
body: <p>i have  <code>[A-NEST BY]</code> and <code>[A-CUT BY]</code> field both are <code>datetime</code> fields why do i get when i run an update </p>
  
  <blockquote>
    <p>Msg 206, Level 16, State 2, Procedure NSTBY, Line 9 Operand type
    clash: date is incompatible with tinyint</p>
  </blockquote>
  
  <pre><code>SET [A-NEST BY] = 
      case DateAdd( day, -10, t1.[A-CUT BY] )
           when 7 then DateAdd( day, -2, t1.[A-CUT BY] )
           when 1 then DateAdd( day, -3, t1.[A-CUT BY])
          else  t1.[A-CUT BY]-10
      end,
  
      FROM WORKORDERS T1
           INNER JOIN inserted i ON T1.[WORK ORDER #] = i.[WORK ORDER #]
          END
  </code></pre>