MYSQL Stored procedure to fetch entire row from a table
You basically don't need a procedure for that.
Procedures get interesting with CURSOR and LOOP when you need &quot;normal&quot; programming besides SQL to makes some thong much more complex
DROP procedure IF EXISTS `proc_get Student`;

DELIMITER $$
CREATE PROCEDURE `proc_get Student` ( IN _student_no BIGINT)
BEGIN
    SELECT * FROM Fetch_Marks WHERE Student_No  = _student_no;
END$$

DELIMITER ;

But I am guessing this is some kind of homework, the variable _student_no is as it is because you have so a optical marker that it is a locally defined variable
Here's another example:
In this, we are adding a second IN variable and in which both are checked if they are NULL or NOT and then selects the wanted data
DROP procedure IF EXISTS `proc_get Student`;

DELIMITER $$
CREATE DEFINER=`root`@`%` PROCEDURE `proc_get Student`( IN _student_no BIGINT,IN _roll_no BIGINT)
BEGIN
    IF ( _student_no IS NOT NULL AND _roll_no IS NULL) THEN
        SELECT * FROM Fetch_Marks WHERE Student_No  = _student_no;
    END IF;
END$$

DELIMITER ;