Question

我正在尝试使用嵌套在游标for循环内的for循环在PLSQL中执行趋势分析。我们的目标是让在2000年至2013年之间，在5年内至少演过8部电影的演员返回。

例如，期望的输出将是：Wahlberg，Mark在2009年至2013年间播放了10部电影。这是我收到的错误：

这是到目前为止我正在使用的代码：

DECLARE
    t movie.yr%TYPE;
    actor_id actor.id%TYPE;
    total INTEGER;
    name actor.name%TYPE;
CURSOR c_actor IS
    select *
    from (select actor.name AS name, count(movie.title) AS total
        from actor, movie, casting
        where movie.id = casting.movie_id
        and actor.id = casting.actor_id
        and movie.yr >= 2000 and movie.yr <=2013
        group by actor.name
        order by count(movie.title) DESC)
    where rownum <= 10;
BEGIN
for v_actor in c_actor
LOOP
    for t in 2000 .. 2009
    LOOP
    select name, total
    into name, total
    from actor, movie
    where movie.yr between t and t+4
    and actor_id = v_actor.actor_id
    and total >= 8
    group by name;
       dbms_output.put_line(name||' played in '||total||' movies between '||t||' and '||t+4);
   END LOOP;
END LOOP;
END;

Answer 1

看来您过于复杂了。这应该起作用：

begin
  for v_actor in (select a.name, count(*) total
                  from actor a join casting c on a.id = c.actor_id
                  join movie m on m.id = c.movie_id
                  where m.yr between 2000 and 2013
                  group by a.name
                  having count(*) >= 8
                 )
  loop
    dbms_output.put_line(v_actor.name ||' acted ' || v_actor.total ||' times');
  end loop;
end;

我认为您在几个小时前提出了一个问题（并将其删除），犯了同样的错误。例如：您创建了一个名为total的变量，并-同时将其放在游标的select语句中。您希望显示由游标获取的值，而不是变量本身，除非游标读取到该变量中-但这是在您从游标显式打开/获取而不是在游标FOR循环中完成的。使用它，您可以使用游标变量并使用它来显示这些值。

Answer 2

您在光标查询中没有得到actor_id。

select *
    from 
   (
    select a.name AS name, count(m.title) AS total
      from actor a
      join casting c 
        on a.id = c.actor_id
      join movie m 
        on m.id = c.movie_id
     where m.yr >= 2000 
       and m.yr <=2013
     group by actor.name
     order by count(movie.title) desc 
   )
   where rownum <= 10;

PLSQL游标循环

2 个答案: