oracle 行转列(用函数和游标完成)

create table students(student_id  varchar2(32),student_name varchar2(180),student_age number)insert into students values('1','金瑞','14');insert into students values('2','中军','15');insert into students values('3','于瑞','14');insert into students values('4','快乐','14');insert into students values('5','刘强','14');insert into students values('6','红豆','14');insert into students values('7','张明','14');insert into students values('8','宿迁','14');insert into students values('9','蓝蝶','14');insert into students values('0','奇美','14');-- 行转列 将多行数据转换为一列。例如学生表中将学生姓名串起来create or replacefunction getStudentNameString  return varchar2 as  begin    declare cursor cu_student is    select student_name from students order by student_id;    student_name varchar2(180);    rowString varchar2(1000);        begin      open cu_student;      fetch cu_student into student_name;      while cu_student%found loop        rowString :=rowString || student_name || ',';        fetch cu_student into student_name;       end loop;       return substr(rowString,1,length(rowString)-1);      end;     end getStudentNameString;-- 测试select getStudentNameString() from dual;-- 代码说明 declare cursor cu_student is select student_name from students order by student_id;用于声明一个游标，该游标可用于循环获得数据表中所有学生姓名记录； fetch cu_student into student_name; 用于将游标所指向的当前记录的数据赋值给student_name；  while cu_student%found loop   用于循环处理游标所指向的记录；   rowString :=rowString || student_name || ','; 用于将变量student_name的值添加到rowString的末尾。