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Student class position generation

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Hello Guys, my name is Royal and i am working a student result grading system which basically calculates students position from a record of averages from a table. So i have a table which contains student details and there rand total and averages from where i wish to get the individual positions. Here is my table record

CREATE TABLE `student_grade` (
  `grade_id` int(11) NOT NULL,
  `class` varchar(255) NOT NULL,
  `term` varchar(255) NOT NULL,
  `year` varchar(255) NOT NULL,
  `name` varchar(255) NOT NULL,
  `admission_no` varchar(255) NOT NULL,
  `grand_total` varchar(255) NOT NULL,
  `student_average` varchar(11) NOT NULL

-- Dumping data for table `student_grade`

INSERT INTO `student_grade` (`grade_id`, `class`, `term`, `year`, `name`, `admission_no`, `grand_total`, `student_average`) VALUES
(2, 'JS1', 'First Term', '2022', 'JUBILEE IHEANACHO', 'LMS1379467', '706', '235.3333333'),
(5, 'JS1', 'First Term', '2022', 'EMMANUEL OKONJI', 'LMS6941511', '723', '241'),
(6, 'JS1', 'First Term', '2022', 'ROYAL NJOKU', 'LMS2805220', '751', '250.3333333');

-- Indexes for dumped tables

-- Indexes for table `student_grade`
ALTER TABLE `student_grade`
  ADD PRIMARY KEY (`grade_id`);

-- AUTO_INCREMENT for dumped tables

-- AUTO_INCREMENT for table `student_grade`
ALTER TABLE `student_grade`

and below  is my code get the position using Mariadb DENSE_RANK function, yet for every student it keeps returning '1' as position where as the averages varies for the 3 student records

$student_class_position = mysqli_query($conn, "SELECT DENSE_RANK() OVER(ORDER BY grand_total DESC) AS d_rank, class, term, year, name, admission_no, grand_total, student_average FROM student_grade") or die(mysqli_error());

$class_position = mysqli_fetch_array($student_class_position);

	if ($class_position['name'] == $grade_name && $class_position['class'] == $grade_class && $class_position['term'] == $grade_term && $class_position['year'] == $grade_year ) {
		$position = $class_position['d_rank'];
echo $position;

Please i need help on this as i have tried even to use RANK() yet same result is still coming up.... also i noticed that if i " SELECT * FROM the table 'student_grade'" and vardumps the data as an array it gives me only the record for the first student record on top. 

attached is the screenshot of my table from phpmyadmin

Your help is needed.


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  • Solution

Here's how I'd do it without the windowing functions

Note: if you have

A 98
B 98
C 95

the A and B a re ranked 1, C is ranked 3.

$grade_class = 'JS1'; 
$grade_name = 'EMMANUEL OKONJI';
$grade_term = 'First Term';
$grade_year  = '2022';
$student_class_position = $conn->prepare( "SELECT rank
                                            FROM (
                                                    SELECT ord.grade_id
                                                         , @seq := @seq+1 as seq
                                                         , @rank := CASE WHEN ord.grand_total = @prev
                                                                        THEN @rank
                                                                        ELSE @seq
                                                                        END as rank
                                                         , @prev := ord.grand_total as grand_total
                                                    FROM (
                                                            SELECT grade_id
                                                                 , g.grand_total
                                                            FROM student_grade g
                                                            ORDER BY grand_total DESC
                                                            LIMIT 18446744073709551615
                                                          ) ord
                                                          JOIN (SELECT @seq:=0, @rank:=0,@prev:=0) init
                                                  ) ranked
                                                  JOIN student_grade g ON g.grade_id = ranked.grade_id
                                            WHERE class = ?
                                                  AND name = ?
                                                  AND term = ?
                                                  AND year = ?
$student_class_position->bind_param('ssss', $grade_class,


echo $position;

I used a prepared statement so user data is not inserted into the query (SQL injection attack prevention)

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