orcle 游标使用

create or replace procedure update_am_pm is
-- 根据time_from列更新ampm为上午或下午，12点为分界线
  cursor ampm_cursor is
    select t.time_from, t.ampm, t.id from usert;
  ampm_c    ampm_cursor%rowtype;
  hour_ampm number;
begin
  for ampm_c in ampm_cursor loop
    hour_ampm := to_number(to_char(ampm_c.time_from, 'hh24'));
    if hour_ampm <= 12 then
      update 
user t set t.ampm='上午' where t.id= ampm_c.id;
    else
      update 
user t set t.ampm='下午' where t.id= ampm_c.id;
    end if;  
  end loop;
end update_am_pm;