title: Problem with mysql query joining three tables
body: <p>I have a problem with a join query, have three tables:
  Calculos which is has a field Operador joined by field "Asignado" related to table Operador, Movimientos which is joined throw IdCaso to Id in Cálculos.
  The problem is that I field Operador gets Null. </p>
  
  <pre><code>SELECT Movimientos.Id as IdMovimientos, 
          Movimientos.Asignado as Operador,Operadores.Id, 
          Operadores.Nombre as Cargo,     
          Movimientos.Fecha,Movimientos.Asignado,
          Movimientos.Estado,Movimientos.Observacion,
          Movimientos.Observacion, 
          Calculos.Nombre,Calculos.Estado,Calculos.Usuario,
          Movimientos.Estado as IdEstado  
  FROM `Calculos` 
      INNER JOIN Movimientos on Movimientos.IdCaso=Calculos.Codigo 
      left JOIN Operadores as Operadores on Calculos.Asignado=Operadores.Id 
  WHERE Calculos.Codigo=4724 
  Order by Fecha Desc
  </code></pre>
  
  <p>Thanks</p>