I don't think there's a particularly good source of info. on this subject in
English, but
a. there are a number of ways you could try constructing "quite a
sophisticated database" without having a software package designed to
develop database applications (such as Access). By which I mean you can set
up a number of tables and use those tables either individually or in
combination as mail merge data sources. For example, you do not actually
need Access to create and populate an Access (Jet) database - you can use VB
or VBA and ADO to do it programmatically. Or you could maintain a database
consisting of a number of tables in plain text format, maintained using e.g.
Notepad.
b. however I think that would really be a very time-consuming and difficult
task - using a software product designed for the job, such as Access, must
surely be a much more simple way to go
c. further, once you have such a product, you may find that it makes sense
to use its reporting facilities to generate at least some of your output
rather than Word, particularly for things which Word mailmerge is not very
good at, such as producing "parent/child (one-many) type output, e.g. one
invoice with a variable number of lines per customer.
d. you probably also need to take a good look at what Word's mailmerge is
capable and not capable of doing "out of the box" before committing to a
particular approach. Beyond a certain level of complexity, you really need
to consider "rolling your own" merge applications using (say) VBA to get,
insert and format the data.