MySql select into与set的区别

见代码：

DROP PROCEDURE IF EXISTS stat_cube.sp_test;

CREATE PROCEDURE stat_cube.`sp_test`( )

BEGIN

  declare dt1,dt2 date default '2011-04-01';

  

  select dt1,dt2;

  

  select day_id into dt1 from stat_cube.dim_dt where 1<>1;

  

  set dt2 = (select day_id from stat_cube.dim_dt where 1<>1);

    

  select dt1,dt2;



END;



call stat_cube.sp_test();

结果 select into 之后的dt1没有值没有变化，还是‘2011-04-01’，而dt2的值变为null。