PL/SQL error "not enough values" during "select into" - oracle

Question

I'm working on creating a pl/sql function that finds the highest average of students from a list of classes. I have the average computation part working correctly; however, I need to return the results as a table of records and I'm running into the error while attempting to store the results into the record.
My record declaration is as follows
create or replace TYPE studentRec as object (
term varchar2(10),
lineNum number(4),
coTitle varchar2(50),
stuId varchar2(5),
average number);
The error comes when I'm trying to fill the record using a select into statement.
create or replace function highest_avg(stu_id scores.sid%type,
line_no scores.lineno%type)
return stuRecTab
as
stuRec stuRecTab;
average number;
studentRec_t studentRec;
begin
stuRec := stuRecTab();
select avg(points)
into average
from scores, courses
where scores.sid = stu_id
and scores.lineno = line_no
and scores.term = courses.term
and scores.lineno = courses.lineno;
SELECT DISTINCT c.term, c.lineno, cc.ctitle, s.sid, average
INTO studentRec_t
from courses c, class_catalog cc, scores s
where s.sid = stu_id
and s.lineno = line_no
and s.term = c.term
and s.lineno = c.lineno
and c.cno = cc.cno;
stuRec := studentRec_t;
return(stuRec);
end;
I've run it as just a query and I'm getting back what I expect so I'm not sure why this error is popping up. Any help would be greatly appreciated as this is my first time working with pl/sql.

Answer 1

First, you can't SELECT INTO the fields of an object instance variable - you have to create an object instance in your select, then SELECT that INTO your object instance variable. You can't simply assign an instance variable to a collection - you need to put it at an appropriate index. So what you end up with is something like:
create or replace function highest_avg(stu_id scores.sid%type,
line_no scores.lineno%type)
return stuRecTab
as
stuRec stuRecTab;
average number;
studentRec_t studentRec;
begin
stuRec := stuRecTab();
select avg(points)
into average
from scores s
inner join courses c
on c.term = s.term and
c.lineno = s.lineno
where s.sid = stu_id and
s.lineno = line_no;
SELECT studentRec(term, lineno, ctitle, sid, average)
INTO studentRec_t
FROM (SELECT DISTINCT c.term, c.lineno, cc.ctitle, s.sid, average
from scores s
INNER JOIN courses c
ON s.term = c.term and
s.lineno = c.lineno
INNER JOIN class_catalog cc
ON cc.cno = c.cno
where s.sid = stu_id and
s.lineno = line_no);
stuRec(1) := studentRec_t;
return(stuRec);
end;
As no test data was provided I haven't tested this - but at least it compiles at dbfiddle.