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

Answer 1

Some more answers to your questions:

1) You're pretty much on target for someone who is approaching a problem like this for the first time. I think the pointers from others on this question thus far pretty much cover it. Good job!

2 & 3) The performance hit you will take will largely be dependent on having and optimizing the right indexes for your particular queries / procedures and more importantly the volume of records. Unless you are talking about well over a million records in your main tables you seem to be on track to having a sufficiently mainstream design that performance will not be an issue on reasonable hardware.

That said, and this relates to your question 3, with the start you have you probably shouldn't really be overly worried about performance or hyper-sensitivity to normalization orthodoxy here. This is a reporting server you are building, not a transaction based application backend, which would have a much different profile with respect to the importance of performance or normalization. A database backing a live signup and scheduling application has to be mindful of queries that take seconds to return data. Not only does a report server function have more tolerance for complex and lengthy queries, but the strategies to improve performance are much different.

For example, in a transaction based application environment your performance improvement options might include refactoring your stored procedures and table structures to the nth degree, or developing a caching strategy for small amounts of commonly requested data. In a reporting environment you can certainly do this but you can have an even greater impact on performance by introducing a snapshot mechanism where a scheduled process runs and stores pre-configured reports and your users access the snapshot data with no stress on your db tier on a per request basis.

All of this is a long-winded rant to illustrate that what design principles and tricks you employ may differ given the role of the db you're creating. I hope that's helpful.

Answer 2

It isn't over-engineered, this is how I would approach the problem. Joining is fine, there won't be much of a performance hit (it's completely necessary unless you de-normalise the database out which isn't recommended!). For statuses, see if you can use an enum datatype instead to optimise that table out.

Answer 3

By the way, it's worth noting that if you're generating CSVs already and want to load them into a mySQL database, LOAD DATA LOCAL INFILE is your best friend: http://dev.mysql.com/doc/refman/5.1/en/load-data.html . Mysqlimport is also worth looking into, and is a command-line tool that's basically a nice wrapper around load data infile.

Answer 4

The only changes I would make are:
1- Change your VARCHAR to NVARCHAR, if you might be going international, you may want unicode.

2- Change your int id's to GUIDs (uniqueidentifier) if possible (this might just be my personal preference). Assuming you eventually get to the point where you have multiple environments (dev/test/staging/prod), you may want to migrate data from one to the other. Have GUID Ids makes this significantly easier.

3- Three layers for your Company -> Division -> Department structure may not be enough. Now, this might be over-engineering, but you could generalize that hierarchy such that you can support n-levels of depth. This will make some of your queries more complex, so that may not be worth the trade-off. Further, it could be that any client that has more layers may be easily "stuffable" into this model.

4- You also have a Status in the Client Table that is a VARCHAR and has no link to the Statuses table. I'd expect a little more clarity there as to what the Client Status represents.

Answer 5

Most things have already been said, but I feel that I can add one thing: it is quite common for younger developers to worry about performance a little bit too much up-front, and your question about joining tables seems to go into that direction. This is a software development anti-pattern called 'Premature Optimization'. Try to banish that reflex from your mind :)

One more thing: Do you believe you really need the 'cities' and 'countries' tables? Wouldn't having a 'city' and 'country' column in the departments table suffice for your use cases? E.g. does your application need to list departments by city and cities by country?

Answer 6

I want to address only the concern that joining to mutiple tables will casue a performance hit. Do not be afraid to normalize because you will have to do joins. Joins are normal and expected in relational datbases and they are designed to handle them well. You will need to set PK/FK relationships (for data integrity, this is important to consider in designing) but in many databases FKs are not automatically indexed. Since they wil be used in the joins, you will definitelty want to start by indexing the FKS. PKs generally get an index on creation as they have to be unique. It is true that datawarehouse design reduces the number of joins, but usually one doesn't get to the point of data warehousing until one has millions of records needed to be accessed in one report. Even then almost all data warehouses start with a transactional database to collect the data in real time and then data is moved to the warehouse on a schedule (nightly or monthly or whatever the business need is). So this is a good start even if you need to design a data warehouse later to improve report performance.

I must say your design is impressive for a first year CS student.