MYSQL := is not a valid at this position, expecting an identifier - mysql

Question

The task is create a stored procedure which creates a statistic of students by city. The result should be like - -
`
delimiter $$
create procedure courcity()
begin
declare list_stud text default '';
declare _cty varchar(50);
declare _count int;
declare _name_stud varchar(50);
declare done integer default FALSE;
declare cty_cur cursor for select cty, count(*) as count from student group by cty order by cty;
declare stud_cur cursor for select name_stud from student where cty = _cty;
declare continue handler for NOT found set done = TRUE;
create temporary table return_table(
cty varchar(50),
count_stud int,
list_stud text default ''
);
begin
declare list_stud text default '';
declare _cty varchar(50);
declare _count int;
declare _name_stud varchar(50);
declare done integer default FALSE;
declare cty_cur cursor for select cty, count(*) as count from student group by cty order by cty;
declare stud_cur cursor for select name_stud from student where cty = _cty;
open cty_cur;
open stud_cur;
read_loop: LOOP
fetch cty_cur into _cty, _count;
IF done THEN
LEAVE read_loop;
read_loop1: loop
fetch stud_cur into _name_stud;
if done then leave read_loop1;
list_stud := list_stud || _name_stud || ', ';//here is the problem
end loop;
close stud_cur;
insert into return_table values (_cty, _count, list_stud);
list_stud := '';
end loop;
close cty_cur;
select * from return_table;
end;$$
delimiter ;
`
Can't create this procedure due to this problem.Can't find mistake.

Answer 1

IF THEN must be closed with END IF;
https://www.mysqltutorial.org/mysql-if-statement/
IF condition THEN
statements;
END IF;
|| is definitely not correct in MySQL. on the right side of := you should have a variable or a valid expression.