Should one web site have about 2 databases? One for content and one for transaction information/customer details?
Or is it sensible to have 2 or 3 databases for web site content? If I use 1 database for all content then some fields will be empty in each entry. If I use 2 databases for content it might be possible to have 0 empty fields.
What issues determine the best choice for number of databases??
Totally dependent upon your site. As you said I would seperate the ordering system into its own db. Website cms into its own and possible include the user system in with it.
How does having multiple or one db affect your table design / empty fields? It shouldn't.
When you say include the user system as well do you mean the user-login/editing aspect of the site??
Would you have the fields:
include these fields in the same database as the CMS? this would mean many empty fields (there will be at least 2,000 products listed so in the user-login part of the database there would be at least 1,995 empty fields).
Are you sure empty fields are not a problem?!!?
I think you mean tables. Yes, you can use multiple tables for your site.
Using multiple databases is a different question . . .
Not too mention I think your confusing columns with rows... I'd do some googling before taking on a project that involves customer orders and private user information storage.
It really depends on which database system you are using. If you are using a full function database where particular users can be granted access to views that only allow them to see what they are supposed to have access to and where they can't access any of the other information at all then you will only need one database.
The only reasons for using a second logical database is if the database you are using does not provide full functionality for security (or does so by your creating multiple logical databases within the physical database) or where you might need to move part of the site functionality to a different server (and therefore need to move the associated database as well.