DB::table() query doubt

Here's how you can write the above SQL query using Laravel's DB::table() facade:

DB::table('exam_application_fees AS ExamFees')
    ->join('students AS Student', 'ExamFees.student_id', '=', 'Student.id')
    ->whereNotIn('Student.student_id', function($query) {
        $query->select('student_id')
            ->from('payments')
            ->where('exammonth_id', '=', 3);
    })
    ->where('ExamFees.exammonth_id', '=', 3)
    ->where('Student.course_id', '=', 3)
    ->update([
        'ExamFees.fine_amount' => 100,
        'ExamFees.total_amount' => DB::raw('ExamFees.total_amount + 100')
    ]);

Explanation:

• We start by calling the DB::table() method and passing in the name of the first table (exam_application_fees) as well as an alias (ExamFees).
• We then join the students table using the join() method and specify the join condition (ExamFees.student_id = Student.id).
• Next, we use the whereNotIn() method to exclude any students who have already made a payment for the given exam month (using a subquery).
• We add two more conditions using the where() method to filter by the exam month and course ID.
• Finally, we call the update() method and pass in an array of column-value pairs to update the fine_amount and total_amount columns. Note that we use the DB::raw() method to add a raw SQL expression for the total_amount column, since we want to increment its value by 100.

I hope this helps! Let me know if you have any questions.