One database or 3 databases?

Anon

I have 3 database-driven dynamic web sites. 1 is already built. 2 others are still in testing. 1 is a consumer sweepstakes site. The other 2 sites are B2B and ecommerce-related.

My question is is having ONE database behind all these sites (i.e. having a global member username/password/email/address) system better thanhaving one database behind each site. I noticed both Yahoo and Lycos are
using the one database approach but not sure if this is the best way to go for me.

I would like to know if having ONE database is indeed the best way or would it cause too much trouble for what it's worth. I.E. A user that registered for the sweepstakes site wants to use his "throw-away" email but he does not want to use his "throw-away" email address when he is using the ecommerce site.

Thanks!

finger

well thats a question of personal favor 🙂
i'd say: if you've the same customers/projects or whathowever in all of the databases: unite them. if this 3 pages are something completely different: seperate them (maintaining them gets much easier IMHO)

regards

finger

[deleted]

Seperate them.
Give every project it's own database.
Why? because sooner or later you are going to split the different sites up.
Don't think you won't, because murphy says you will.

jordanj

Frankly, I would say keep them separate just because of the fact that I am an optimist and that I believe the end goal is to have a large user base. Once your user base gets so big, it would be easier to maintain this on separate db's.. but then again, I might be talking out my bung hole.

Anon

Thanks for the responses everybody. Here is a more in-depth look at the problem:

The 3 sites are somewhat connected. The first site (which is currently live) is a content site. The second site (which is going live at the end of February) is a webmaster affiliate site that will recruit webmasters to drive users to site #1. However, the second site will also eventually be used to drive traffic to site #3, which is an ecommerce site.

REASONS FOR ONE DATABASE

I have built various scripts and tools that would apply to all three sites. For example, the mailing list manager and the ad manager.
Putting the three sites on separate databases would mean that I have to rewrite the managers for each database.

Also, putting the three sites on separate databases would mean there will be some duplication of data as some users will have registered already for one site but now have to register again for another site.

Last but not least, many of the web's largest sites seem to be using a primary database for all of its users. Take Yahoo, Lycos and Go2Net for example, there is a unified login for almost all of Yahoo's sites. You only need 1 Yahoo ID to access just about all of Yahoo's services (even geocities after it was bought by Yahoo).
I am sure that Yahoo does NOT store the same information on its users (probably 60 million plus?) in multiple databases. And I don't think the size of the data would make Yahoo split its users into multiple databases.

Even if one database were to be used for all sites, it seems to me that it would be easier to later on split the databases up then to combine three databases (one user might have different ids and passwords in various sites).

REASONS FOR HAVING THREE DATABASES

Sometimes people might want to give different info for different sites. For example, a person might want to give the content site a "throw-away" email address but he will want to give a "work-address" for the webmaster affiliate site. So having one database would cause certain restrictions on choices of input of data.

IS THERE A BETTER WAY?

To the database gurus out there, is there a better way to solve this problem? Is there a way to take advantage of the tools I have built for the first site already by including all the sites into one database but at the same time overcome the restrictions on the user's choice of input of data?

Thank you and best wishes.

[deleted]

About the yahoo example;
The fact that you can access many sites using the same login says nothing at all about what they are doing at their end.
They might have 10 different databases that replicate the data to eachother, or 26 (alphabetically, one for names starting with A, etc.)
You'll never know from just using the web.

In general, there is nothing you can do with one database that you can't do with three.
It's all down to the tables and what you store in them.
Where the tables are stored doesn't really matter much to the database engine. (within limits ofcourse) Even MySQL is capable of selecting data from multiple databases at the same time...

The main thing to consider is: what does the future hold?
Will your setup with one database survive when it grows to huge/gigantic proportions?

Changing your setup now is easy because everything is still small.
But what if your site grows too big to hold in one database (in MySQL this is a real threat on some setups).
What if your database server becomes too slow to handle the queries and you want to expand? Adding another server and moving one database over to it is easy, but creating a database that runs on two servers at the same time gets more difficult.