SELECT a.tipo_cliente,a.sec_cliente,b.nombre,b.limite_credito,SUM(a.neto) 
      FROM vetb00002 a,vetb00004 b 
      WHERE a.status_t IS NULL AND a.fecha_factura between "01101999" AND "23022000"  AND 
            a.tipo_cliente = b.tipo_cliente and 
            a.sec_cliente = b.sec_cliente AND b.status_t IS NULL  
       and  a.ventas = '1' 
      GROUP BY 1,2,3,4 ORDER BY 5 DESC,1,2