Database design for attendance feature

database-designdatabase-recommendation

My app has a requirement wherin we need to capture attendance details of a class. A class typically has 50-60 students and there will be records with attendance/absense status of each student for a day.

My idea is having a table like this:

| student_id | class | section | date       | status      |
------------------------------------------------------------
| 2          | 7     |     A   | 2013-10-24 | 1 or X      |

X – Absent , 1 – Present

This would have records for all months for all students across all classes. So 1000 students, 30 record per student per month, this table must be ending with 1000*30*12 = 360,000 records. We'll be pulling attendance report student-wise and class-wise.

My friend has a suggestion to create a table for each year which would look like this:

| student id  | class   | section | month  | date1 | date 2 | date 3 |......| date30 |
--------------------------------------------------------------------------------------
| 1           | 2       |     C   | Jan    | X or 1|  X or 1| X or 1 |      |X or 1  |

This would mean that I'll have the attendance details of each student for a month in a single record. There would be 1000 (student) * 12 (months) = 12000 records only for an year

Please suggest which would be more suitable here, and if there's any other better way of doing it.

Thanks.

Best Answer

I would suggest something different than you have here- a separate table to record the student_class relation:

| student_id | class | date       | 
-----------------------------------
| 2          | 7     | 2013-10-24 |

This would have one record for a student where a class was attended. For each class and date for which there is no record, it can be seen that the student did not attend.

If you want to further normalize the design, I would suggest instead three new tables:

Student_Class: (to determine enrolled students)

| class | student_id     | 
--------------------------
| 1     | 2              |

Class_Date: (class_date_id surrogate key for pk(class, date)) (to determine dates classes were held)

| class_date_id | class | date       | 
-----------------------------------
| 1             | 7     | 2013-10-24 |

Student_Class_Date: (to determine which students attended which class period)

| class_date_id | student_id     | 
----------------------------------
| 1             | 2              |

This would allow you to easily define which classes were held on which date, easy updating etc.

Edit: Added additional detail with student_class implied relation from question context

Related Solutions

Sql-server – Data Model For Summarizing Student Info

Calculate those counts on the fly.

For most data sets of this nature, I would imagine calculating the count of tardiness events would be relatively cheap. How many rows do you expect there to be in the long run in your students or attendance tables? Probably on the order of tens of thousands at most. Contrast that to calculating an account balance from its transaction history in database for a large bank with billions of transactions. In this case I would consider persisting a summary of these aggregations somewhere.

If you wanted to pre-calculate this data anyway, I would summarize the count of tardiness events per student per year in an indexed view as suggested in the top answer here.

For example:

CREATE VIEW dbo.tardiness_summary
WITH SCHEMABINDING
AS
SELECT
     student_id
   , year
   , COUNT_BIG(*) AS tardy_count
FROM dbo.attendance
GROUP BY 
     student_id
   , year
;

CREATE UNIQUE CLUSTERED INDEX IX_tardiness_summary
ON dbo.tardiness_summary (
     student_id
   , year
;

This is not a flexible approach, however, as this view is now schema-bound to the base tables and thus any modifications to either the view or the table will require rebuilding the view. Indexed views also have many restrictions on how they may be created or queried. Their advantage is that they guarantee the summary table will stay in sync with its sources because the database engine is now doing this work for you.

Database schema design for school system

To your specific question of (easily satisfied) plausibility, the answer is yes. Since you seem to be looking for a broader critique. You seem to be mostly on the right track, but a few things are making your description overly complex.

It looks like your Classes table is more like what I would consider a course to be and your departments_teachers_and_classes is more of what I would expect a Classes table to be. A course would be Math, but a class would be the Math course taught by a particular teacher during a particular school term. A class is like an instance of a course.

To carry this change through, your departments_teachers_classes_and_students could simply be ClassStudents.

It seems as though you are using the department concept on several different levels. You should decide where the department belongs and stop referencing it everywhere else. You've said that a teacher can teach for multiple departments, so we can't put the department in the teachers table. This leaves Classes and Courses. Whichever you decide, it need only have a foreign key to the Departments table (unless you decide that one can be in multiple Departments). This eliminates the Departments_and_teachers table.

Teachers_and_Students could be replaced with a teacher foreign key in the Classes table and students/classes foreign keys in a ClassStudents table.

In short, for the portion of the design you have described, you probably need the following tables:

Departments
Teachers
Students
Courses
Classes
ClassStudents
Terms

Best Answer

Related Solutions

Sql-server – Data Model For Summarizing Student Info

Database schema design for school system

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