First-time database design: am I overengineering? [closed]

Answer 1

You've got the right idea. You can however clean it up, and remove some of the mapping (has*) tables.

What you can do is in the Departments table, add CityId and DivisionId.

Besides that, I think everything is fine...

Answer 2

I've worked in the training / school domain and I thought I'd point out that there's generally a M:1 relationship between what you call "sessions" (instances of a given course) and the course itself. In other words, your catalog offers the course ("Spanish 101" or whatever), but you might have two different instances of it during a single semester (Tu-Th taught by Smith, Wed-Fri taught by Jones).

Other than that, it looks like a good start. I bet you'll find that the client domain (graphs leading to "clients") is more complex than you've modeled, but don't go overboard with that until you've got some real data to guide you.

Answer 3

No. It looks like you're designing at a good level of detail.

I think that Countries and Companies are really the same entity in your design, as are Cities and Divisions. I'd get rid of the Countries and Cities tables (and Cities_Has_Departments) and, if necessary, add a boolean flag IsPublicSector to the Companies table (or a CompanyType column if there are more choices than simply Private Sector / Public Sector).

Also, I think there's an error in your usage of the Departments table. It looks like the Departments table serves as a reference to the various kinds of departments that each customer division can have. If so, it should be called DepartmentTypes. But your clients (who are, I assume, attendees) do not belong to a department TYPE, they belong to an actual department instance in a company. As it stands now, you will know that a given client belongs to an HR department somewhere, but not which one!

In other words, Clients should be linked to the table that you call Divisions_Has_Departments (but that I would call simply Departments). If this is so, then you must collapse Cities into Divisions as discussed above if you want to use standard referential integrity in the database.

Answer 4

Following comments based on role as a Business Intelligence/Reporting specialist and strategy/planning manager:

1. I agree with Larry's direction above. IMHO, It's not so much over engineered, some things just look a little out of place. To keep it simple, I would tag client directly to a Company ID, Department Description, Division Description, Department Type ID, Division Type ID. Use Department Type ID and Division Type ID as references to lookup tables and internal reporting/analysis fields for long term consistency.

2. Packs table contains "Credit" column, shouldn't that actually be tied to the Client base table so if they many packs you can see how much credit owed is left for future classes? The application can take care of the calc and store it centrally in the Client table.

3. Company info could use many more fields, including the obvious address/phone/etc. information. I'd also be prepared to add in D&B "DUNs" columns (Site/Branch/Ultimate) long term, Dun and Bradstreet (D&B) has a huge catalog of companies and you'll find later down the road their information is very helpful for reporting/analysis. This will take care of the multiple division issue you mention, and allow you to roll up their hierarchy for sub/division/branches/etc. of large corps.

4. You don't mention how many records you'll be working with which could imply setting yourself up for a large development initiative which could have been done quicker and far fewer headaches with prepackaged "reporting" software. If your not dealing with a large database (< 65000) rows, make sure MS-Access, OpenOffice (Base) or related report/app dev solutions couldn't do the trick. I use Oracle's free APEX software quite a bit myself, it comes with their free database Oracle XE just download it from their site.

5. FYI - Reporting insight: for large databases, you typically have two database instances a) transaction database for recording each detailed record. b) reporting database (data mart/data warehouse) housed on a separate machine. For more information search google both Star Schema and Snowflake Schema.

Regards.

Answer 5

A few things came to mind:

1. The tables seemed geared to reporting, but not really running the business. I would think when a client signs up, there's essentially an order being placed for the client attending a list of sessions, and that order might be for multiple employees in one company. It would seem an "order" table would really be at the center of your system and driving your data capture and eventual reporting. (Compare the paper documents you've been using to run the business with your database design to see if there's a logical match.)

2. Companies often don't have divisions. Employees sometimes change divisions/departments, maybe even mid-session. Companies sometimes add/delete/rename divisions/departments. Make sure the possible realtime changing contents of your tables doesn't make subsequent reporting/grouping difficult. With so much contact data split over so many tables, you might have to enforce very strict data entry validation to keep your reports meaningful and inclusive. Eg, when a new client is added, making sure his company/division/department/city match the same values as his coworkers.

3. The "packs" concept isn't clear at all.

4. Since you indicate it's a small business, it would be surprising if performance would be an issue, considering the speed and capacity of current machines.