First-time database design: am I overengineering?

# Background # I'm a first year CS student and I work part time for my dad's small business. I don't have any experience in real world application development. I have written scripts in Python, some coursework in C, but nothing like this. My dad has a small training business and currently all classes are scheduled, recorded and followed up via an external web application. There is an export/"reports" feature but it is very generic and we need specific reports. We don't have access to the actual database to run the queries. I've been asked to set up a custom reporting system. My idea is to create the generic CSV exports and import (probably with Python) them into a MySQL database hosted in the office every night, from where I can run the specific queries that are needed. I don't have experience in databases but understand the very basics. I've read a little about database creation and normal forms. We may start having international clients soon, so I want the database to not explode if/when that happens. We also currently have a couple big corporations as clients, with different divisions (e.g. ACME parent company, ACME healthcare division, ACME bodycare division) The schema I have come up with is the following: 1. **From the client perspective:** * Clients is the main table * Clients are linked to the department they work for * Departments can be scattered around a country: HR in London, Marketing in Swansea, etc. * Departments are linked to the division of a company * Divisions are linked to the parent company 2. **From the classes perspective:** * Sessions is the main table * A teacher is linked to each session * A statusid is given to each session. E.g. 0 - Completed, 1 - Cancelled * Sessions are grouped into "packs" of an arbitrary size * Each packs is assigned to a client I "designed" (more like scribbled) the schema on a piece of paper, trying to keep it normalised to the 3rd form. I then plugged it into MySQL Workbench and it made it all pretty for me:<br> ([Click here for full-sized graphic][1]) [![alt text][2]][2] <sub>(source: [maian.org](http://maian.org/img/schema.png))</sub> ## Example queries I'll be running ## * Which clients with credit still left are inactive (those without a class scheduled in the future) * What is the attendance rate per client/department/division (measured by the status id in each session) * How many classes has a teacher had in a month * Flag clients who have low attendance rate * Custom reports for HR departments with attendance rates of people in their division # Question(s) # * **Is this overengineered or am I headed the right way?** * Will the need to join multiple tables for most queries result in a big performance hit? * I have added a 'lastsession' column to clients, as it is probably going to be...