Searching records in a relational database - php

Question

Scenario:
I am working on a PHP/MySQLi aplplication where I have got 2 tables attendance and students .
students has fields: student_id, fullname, phone,email,gender, department and level.
attendance table has fields: attendance_id, student_id, department_id, level_id.
I was able to fetch all students whose records are in the attendance table according to their department and level.
Question:
Let's assume that I was able to fetch all students whose records are in the attendance table and are in 200L (with level_id, 2) computer science (with department_id, 4) department, if the list of the students present are much and it was paginated and I want to search for a particular student's fullname that's in attendance table in reference to student's table.
How will the SQL query be like? I tried the following query which didn't work.
$search_query = mysqli_query($db_connect, "SELECT *FROM attendance WHERE student_id=\"SELECT student_id FROM students WHERE fullname LIKE '%$student_fullname%'\";
Please help.

Answer 1

Try this query:
SELECT attendance.*
FROM `students`
INNER JOIN `attendance`
ON `attendance`.`student_id` = `students`.`student_id`
WHERE `students`.`fullname` LIKE `%$student_fullname%`
I know that may look back-to-front at first, but I prefer to structure the SQL to show the strong selector (the LIKE filter) in the WHERE clause. If you do not like that, you can get the same result like this:
SELECT attendance.*
FROM `attendance`
INNER JOIN `students`
ON `students`.`student_id` = `attendance`.`student_id`
AND `students`.`fullname` LIKE `%$student_fullname%`
Note that this second version does NOT have a WHERE clause - always put filters on the RHS of a join in the join's ON clause, because otherwise outer joins will not behave correctly.

Answer 2

The SQL query you are looking for is:
select * from attendance join students on attendance.student_id = students.student_id where students.fullname like '%NAME%'
so in PHP you would need something like:
$query_string = "select * from attendance join students on attendance.student_id = students.student_id where students.fullname like '%$student_fullname%'";
$search_query = mysqli_query($db_connect, $query_string);
I would recommend you to have a look at prepared statements though, to prevent SQL injection: http://php.net/manual/en/mysqli.prepare.php
/* create a prepared statement */
$query_string = "select * from attendance join students on attendance.student_id = students.student_id where students.fullname like ?";
if ($stmt = $mysqli->prepare($query_string)) {
$stmt->bind_param("s", $student_fullname);
$stmt->execute();
$result = $stmt->get_result();
while ($myrow = $result->fetch_assoc()) {
// use your $myrow array as you would with any other fetch
printf("%s found in attendance record ID: %s\n", $student_fullname, $myrow['attendance_id']);
}
$stmt->close();
}