while 语句写法:

        while '条件' do

                循环体语句;

        end while;

完整写法:

drop procedure if exists aaa;
DELIMITER $$
create procedure aaa( out a varchar(100), out b varchar(500) )
TOP:
 begin
   declare v_name varchar(1000);#用户名
   set v_name = '张三';
   if(a>0) then
      v_name = '李四';
              while '条件' do
                       循环体语句;
               end while;
    end if;
end$$
DELIMITER;

注意事项:“;” 一定要用英语输入法的