Question

创建了一个记录类型 - trec
然后创建了一个上述记录类型为abc的表v1
使用游标，加载的学生，课程，使用fetch和loop将多个表中的数据分数到表类型v1中。
现在我想从v1计算一个特定的平均分数。

可以建议如何对t_tab

set serveroutput on;
declare 
    type t_rec is record
    (
      student_id number,
      course_id number,
      grade number
    );
    error_msg varchar2(50);
    type abc is table of t_rec index by binary_integer;
    v1 abc;
    x number;
    cursor st_gr
    is 
      with sf as
      (
        select s.student_id as student_id, count(cr.course_id)as no_of_courses
        from grade g, student s, class cs, course cr
        where g.student_id = s.student_id
        and cs.course_id = cr.course_id
        and g.class_id = cs.class_id
        group by s.student_id
      )
      select x.student_id as student_id, cr.course_id as course_id, g.score as grade
      from sf x, grade g, class cs, course cr
      where x.no_of_courses>4 
      and x.student_id = g.student_id 
      and cs.course_id = cr.course_id
      and g.class_id = cs.class_id;

      i binary_integer :=0;
      temp binary_integer :=0;
begin
      open st_gr;
      loop
        i:=i+1;
        fetch st_gr into v1(i);
        exit when st_gr%notfound;
      end loop;
      close st_gr;
        dbms_output.put_line('students who enrolled in more than 4 courses');  
        dbms_output.put_line('student_id'||'    '||'course_id'||'          '||'grade');  
      select student_id, avg(grade)
      from v1
      group by student_id;
end;

Answer 1

是否有理由不在查询中选择它？

select x.student_id as student_id, cr.course_id as course_i
     , g.score as grade, AVG(g.score) OVER (PARTITION BY x.student_id) as avg_score
 from sf x, grade g, class cs, course cr
where x.no_of_courses>4 
  and x.student_id = g.student_id 
  and cs.course_id = cr.course_id
  and g.class_id = cs.class_id;

这将在您的记录中添加一个名为avg_score的新字段，其中包含给定学生的平均分数。

编辑：或者，您可以为记录结构创建数据库级别TYPE声明。如果要在对象类型上使用DML，则必须在数据库级别而不是PL / SQL级别创建它，因为数据库不知道PL / SQL定义的类型。

CREATE OR REPLACE TYPE t_rec AS OBJECT
(
  student_id number,
  course_id number,
  grade number
);

CREATE OR REPLACE TYPE abc AS TABLE OF t_rec;

然后，在您的代码中：

FOR Rec IN (SELECT student_id, AVG(grade) avg_grade 
              FROM TABLE ( cast( v1 as abc) )
             GROUP BY student_id) 
LOOP
   dbms_output.put_line(Rec.student_id, Rec.avg_grade);
END LOOP;

完全未经测试。不过，这是一般的想法。

对表类型中的数据执行计算

1 个答案: