批量更新操作oracel语句

BEGIN
  FOR cur IN (
      SELECT b.dm,b.mc FROM xxx b 
    ) loop 
  UPDATE xxx s SET s.dm= cur.dm  where s.mc is not null and  s.dm is null and cur.mc= s.mc
  END loop;
END;

BEGIN
    FOR L_RECORD IN ( 
    SELECT a.* FROM GBT_BATTERYTRACE_WR a WHERE a."modulecode" IN ( SELECT DISTINCT        
    MODULECODE FROM GBT_BATTERYTRACE )
)
LOOP
    UPDATE GBT_BATTERYTRACE x SET x.PACKCODE = L_RECORD."packcode" 
    WHERE x.MODULECODE = L_RECORD."modulecode";

END LOOP;
END;