How can I make this database schema better?

Question

I currently have two tables in which stores the attendances of a student in a course. I have the hub_attendance table which stores the total attendances of a student and the hub_attendance_lesson where it stores the attendance of each lesson that a student has or has not attended. I'm not sure if this is correct or if I'm doing anything wrong, I'm a beginner in databases!

hub_attendance:
id
student_id
course_id
total_lessons
total_lessons_so_far
total_attended
total_absent
total_excused_absent
total_late
total_excused_late

hub_attendance_lesson:
id
lesson_id
course_id
student_id
date
attended
absent
excused_absent
late
excused_late

EDIT:

So I've gotten rid of the first table completely and this is my new single table.

Hub_Attendance:
id
lesson_id
course_id
student_id
date
attendance

Answer 1

As Dutchie432 said, you don't need the first table because it introduces unnecessary redundancy and you can count those statistics on the fly. Such aggregate tables can be a good solution if performance is an issue, but they should be used only as a last resort.

About the second table - you have separate fields attended , absent , excused_absent , late and excused_late . Aren't these mutually exclusive? So only one of them can be true for one row? If so, you may be better off with one enumeration field called for example attendance , which would take different values for each of those states. In that way you could't have rows where none of the flags, or more than one flag, is set.

Answer 2

Here's what you need:

**Course**
id, name, etc...

**Lesson**
id, courseid, name, etc...

**Attendance**
id, studentid, lessonid, lateness, etc...

**Enrolment**
id, courseid, studentid, startdate, etc...

You need the enrolment table to know that students should be on a course even if they never turn up for lessons. The attendance table will allow you to have many students per lesson and many lessons per student. This is a many-to-many table . Any aggregation and counting can be done in SQL.

Answer 3

If I understand your schema correctly, Your first table can be totally eliminated. You should be able to fetch the totals using MySQL.

select count(id) as total_late from hub_attendance_lesson where late=true and student_id=TheUserId 

Answer 4

Remove this first table, every total can be fetch using SQL :

SELECT count(id) AS absent
FROM hub_attendance_lesson 
WHERE lesson_id = <your lesson id>
AND absent = <false / true>

I guess you'll be able to adapt this code for your needs.