Oracle SQL function using Select Count returns duplicate answer for every row

Trying to do a simple User function where I get the number of people whos age is > 100.

this is my current table

select * from peoples

**NAME**      **AGE**
----------------------
Joe Bloggs  12
Paul Smith  15
Jonah James 534
Mika Rive   31
Hannah Bananas  56
Harry Heelz 4
Brian Bolton    232
Jack Ripper 123

I’m currently trying to implement user function where the output is a single row with the total number of people with an age greater than 100.

Here is the function I have attempted to make

create or replace function agetest return number is
v_count number;

begin
    select count(age) into v_count
    from persons
    where  age > 100;
    
        return v_count;
end;
 

When I execute the SQL query directly I get the correct answer

select count(age) from persons where age > 100;

but when I run the function

select agetest from persons;

I get the output of:

Just looking for guidance on why the output is showing the same result for each row.

My ideal output for the function would just be:

>Solution :

Try executing the function against DUAL:

SELECT agetest FROM dual;

In Oracle, the DUAL table is a sort of dummy table which has only one record in it.