PLSql -- 练习2 cursor 显式/隐式游标

问题

统计列出矩阵类型各分数段人数，横轴为分数段[100-85]、[85-70]、[70-60]、[<60]，纵轴为课程号

解决此问题的SQL语句见  Sql – 练习2 统计列出矩阵类型各分数段人数

解决1

分析

--Sql 
 select distinct sc.course_no from hand_student_core sc  ;
 -- cursor cno -> exit when nofound
 select sc.core from hand_student_core sc where sc.course_no='c001';
 -- cursor core(no)  --> exit when  nofound
-- using variable
cnum1,cnum2,cnum3,cnum4
cno_tmp

declare
  cnum1 number;
  cnum2 number;
  cnum3 number;
  cnum4 number;
  cursor cno is
    select distinct sc.course_no from hand_student_core sc;
  cursor sccore(cno_tmp hand_student_core.course_no%type) is
    select sc.core from hand_student_core sc where sc.course_no = cno_tmp;
  c_no    hand_student_core.course_no%type;
  sc_core hand_student_core.core%type;

begin
  dbms_output.put_line('course_no  [100-85]   [85-70]   [70-60]   [<60]');
  open cno;
  loop
    fetch cno
      into c_no;
    exit when cno%Notfound;
    cnum1 := 0;
    cnum2 := 0;
    cnum3 := 0;
    cnum4 := 0;
    open sccore(c_no);
    loop
      fetch sccore
        into sc_core;
      exit when sccore%NOTFOUND;

      if sc_core >= 85 and sc_core < 100 then
        cnum1 := cnum1 + 1;
      elsif sc_core >= 70 and sc_core < 85 then
        cnum2 := cnum2 + 1;
      elsif sc_core >= 60 and sc_core < 75 then
        cnum3 := cnum3 + 1;
      else
        cnum4 := cnum4 + 1;
      end if;
    end loop;
    close sccore;
    dbms_output.put_line('    ' || c_no || '             ' || cnum1 ||
                         '              ' || cnum2 || '            ' ||
                         cnum3 || '            ' || cnum4);
  end loop;
  close cno;
exception
  when no_data_found then
    dbms_output.put_line('no data found');
  when others then
    dbms_output.put_line('others');
end;

解决2

隐式游标

declare
  cnum1 number;
  cnum2 number;
  cnum3 number;
  cnum4 number;
  c_no  hand_student_core.course_no%type;
begin
  dbms_output.put_line('course_no  [100-85]   [85-70]   [70-60]   [<60]');

  for result_cno in (select distinct course_no from hand_student_core) loop

    cnum1 := 0;
    cnum2 := 0;
    cnum3 := 0;
    cnum4 := 0;
    c_no  := result_cno.course_no;

    for result_core in (select sc.core
                          from hand_student_core sc
                         where sc.course_no = c_no) loop

      if result_core.core >= 85 and result_core.core < 100 then
        cnum1 := cnum1 + 1;
      elsif result_core.core >= 70 and result_core.core < 85 then
        cnum2 := cnum2 + 1;
      elsif result_core.core >= 60 and result_core.core < 75 then
        cnum3 := cnum3 + 1;
      else
        cnum4 := cnum4 + 1;
      end if;
    end loop;

    dbms_output.put_line('    ' || c_no || '             ' || cnum1 ||
                         '              ' || cnum2 || '            ' ||
                         cnum3 || '            ' || cnum4);  end loop;

exception
  when no_data_found then
    dbms_output.put_line('no_data_found');
  when others then
    dbms_output.put_line('others');
end;

结果