order by not working properly in mysql

this is my select query i want in order by with transType = 'I' and after that with transdate in ascending order throw that query i can get transType = 'I' record properly but after that it shows me not proper sequence.

  SELECT tranjectionId,date_format(transDate,'%d-%m-%Y') AS transDate,motiAmount,
                             transType,tranjection.partyId,item.itemName,gwt,loss,netwet,
                              party.partyName,melting,westage,finewet,rhodium,amount,bhav 
                         FROM  tranjection,party,item
                       WHERE party.partyId =  tranjection.partyId
                       AND item.itemId =  tranjection.itemId
                         AND tranjection.partyId = ".$partyId."
                        ORDER BY  (transType = 'R') DESC,
                                   transDate