SQL MIN() smaller/greater not working properly - sql

Question

I have this Data in DB
CREATE TABLE Stu_Table
(
Stu_Id VARCHAR(2),
Stu_Name VARCHAR(15),
Stu_Class VARCHAR(10),
sub_id VARCHAR(2),
marks VARCHAR(3)
);
INSERT INTO Stu_Table VALUES (1, 'Komal', 10, 1, 45);
INSERT INTO Stu_Table VALUES (2, 'Ajay', 10, 1, 56);
INSERT INTO Stu_Table VALUES (3, 'Rakesh', 10, 1, 67);
INSERT INTO Stu_Table VALUES (1, 'Komal', 10, 2, 47);
INSERT INTO Stu_Table VALUES (2, 'Ajay', 10, 2, 53);
INSERT INTO Stu_Table VALUES (3, 'Rakesh', 10, 2, 57);
INSERT INTO Stu_Table VALUES (1, 'Komal', 10, 3, 45);
INSERT INTO Stu_Table VALUES (2, 'Ajay', 10, 3, 56);
INSERT INTO Stu_Table VALUES (3, 'Rakesh', 10, 3, 67);
INSERT INTO Stu_Table VALUES (1, 'Komal', 10, 4, 65);
INSERT INTO Stu_Table VALUES (2, 'Ajay', 10, 4, 56);
INSERT INTO Stu_Table VALUES (3, 'Rakesh', 10, 4, 37);
INSERT INTO Stu_Table VALUES (1, 'Komal', 10, 5, 65);
INSERT INTO Stu_Table VALUES (2, 'Ajay', 10, 5, 46);
INSERT INTO Stu_Table VALUES (3, 'Rakesh', 10, 5, 63);
And I'm doing this query on this data.
SELECT *
FROM
(
SELECT
Stu_Id,
MIN(marks) AS mini,
AVG(marks) AS per
FROM stu_table
GROUP BY stu_id
HAVING MIN(marks) > 45
);
And I'm getting this:
Stu_Id| mini | per
1 | 45 | 53.4
2 | 46 | 53.4
3 | 37 | 58.2
I don't understand why I still see Stu_Id 1 with min(mark)=45 when I clearly have this HAVING min(marks)>45 in my query.
Runnable Demo
FIX:
Thanks to #sybkar and #Martin Smith!
I set the marks type as a string.
It's should be INT...
Thanks guys!
Working perfect!
create table Stu_Table(Stu_Id INT(2), Stu_Name varchar(15),
Stu_Class varchar(10),sub_id INT(2),marks INT(3));<--INT!!!

Answer 1

I don't understand why I still see Stu_Id 1 with min(mark)=45
when I clearly have this HAVING min(marks)>45 in my query.
You don't. Or at the least the demo you have provided doesn't.
In general any weird results that you are getting will be because marks is being stored as a string so MIN(marks) will be bringing back the earliest in alphabetical order though.
For example HAVING MIN(marks) > 45 will also bring back 5, 6, 7, 8 and 9