How to display the frequency count in several mysql tables in codeigniter - php

Question

How can I display the frequency of the number of students in a class. I have several tables in the database.
table = kelas
+----+---------+---------+
| id | tingkat | nama |
+----+---------+---------+
| 1 | 5 | Kelas 5 |
| 2 | 3 | Kelas 3 |
+----+---------+---------+
table = siswa
+----+----------+
| id | nama |
+----+----------+
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 1 |
etc.
table = kelas_siswa
+----+----------+----------+------+
| id | id_kelas | id_siswa | ta |
+----+----------+----------+------+
| 18 | 1 | 18 | 2019 |
| 19 | 1 | 19 | 2019 |
| 20 | 1 | 20 | 2019 |
| 21 | 1 | 21 | 2019 |
| 22 | 1 | 22 | 2019 |
| 23 | 1 | 23 | 2019 |
| 24 | 1 | 24 | 2019 |
| 25 | 1 | 25 | 2019 |
| 26 | 1 | 26 | 2019 |
| 27 | 1 | 27 | 2019 |
| 28 | 1 | 28 | 2019 |
| 29 | 1 | 29 | 2019 |
| 30 | 1 | 30 | 2019 |
| 31 | 1 | 31 | 2019 |
| 1 | 2 | 1 | 2019 |
| 2 | 2 | 2 | 2019 |
| 3 | 2 | 3 | 2019 |
| 4 | 2 | 4 | 2019 |
| 5 | 2 | 5 | 2019 |
| 6 | 2 | 6 | 2019 |
| 7 | 2 | 7 | 2019 |
| 8 | 2 | 8 | 2019 |
| 9 | 2 | 9 | 2019 |
| 10 | 2 | 10 | 2019 |
| 11 | 2 | 11 | 2019 |
| 12 | 2 | 12 | 2019 |
| 13 | 2 | 13 | 2019 |
| 14 | 2 | 14 | 2019 |
| 15 | 2 | 15 | 2019 |
| 16 | 2 | 16 | 2019 |
| 17 | 2 | 17 | 2019 |
+----+----------+----------+------+
How do I display data on the number of students for kelas 3 and kelas 5. on :
.$JUMLAH_SISWA.
For example Class 3 there are 17 students and Class 5 there are 14 Students
public function index() {
$d=array();
$ambil_data_kelas = $this->db->query("SELECT id, nama FROM m_kelas ORDER BY tingkat ASC, nama ASC")->result_array();
$tampil = "";
if (!empty($ambil_data_kelas)) {
foreach ($ambil_data_kelas as $v) {
$tampil .= '<div class="col-md-4"><div class="panel panel-info">
<div class="panel-heading"><b>'.$v['nama'].' jumlah siswa : '.$JUMLAH_SISWA.'</b></div>
<div class="panel-body" style="height: 300px; overflow: auto">
<table class="table table-stripped">
<thead>
<tr><th>No</th><th>Nama</th><th>Aksi</th></tr>
</thead>
<tbody>';
$q_siswa_per_kelas = $this->db->query("SELECT
a.id, b.nama nmsiswa, a.id_kelas
FROM t_kelas_siswa a
INNER JOIN m_siswa b ON a.id_siswa = b.id
WHERE a.id_kelas = '".$v['id']."'
AND a.ta = '".$this->d['ta']."'
ORDER BY b.nis ASC, b.nama ASC")->result_array();
if (!empty($q_siswa_per_kelas)) {
$no = 1;
foreach ($q_siswa_per_kelas as $k) {
$tampil .= '<tr><td>'.$no++.'</td><td>'.$k['nmsiswa'].'</td><td class="ctr"><i class="fa fa-remove"></i></td></tr>';
}
}
$tampil .= '</tbody></table></div></div></div>';
}
}
$this->d['tampil'] = $tampil;
$this->d['p'] = "list";
$this->load->view("template_utama", $this->d);
}

Answer 1

To count the number of students in each class you only need:
SELECT id_kelas, COUNT(*) 'count'
FROM kelas_siswa
GROUP BY id_kelas
and then you can bolt on additional JOINs to include whatever else you need like class metadata.
Eg:
SELECT ks.id_kelas, k.name, COUNT(*) 'count'
FROM kelas_siswa ks INNER JOIN kelas k
ON ks.id_kelas = k.id
GROUP BY ks.id_kelas
Or getting fancy:
SELECT ks.id_kelas, k.name, COUNT(*) 'count', GROUP_CONCAT(s.nama) 'students'
FROM kelas_siswa ks INNER JOIN kelas k
ON ks.id_kelas = k.id
INNER JOIN siswa s
ON ks.id_siswa = s.id
GROUP BY ks.id_kelas
Which will also list all the student names along with the count.