Thanks villas and Ivan. When I say joins I mean 1:1 relationships (or "linked tables"?), where each record in tables A/B/C reference one (and only one) unique 'entity' record, kind of like an 'extension' of such tables, but with data centralized in the 'entity' table (which would allow better maintenance).
I know I have the alternative of embedding all of the 'entity' fields directly into tables A/B/C (instead of having a separate centralized 'entity' table, with 1:1 relationships). I was wondering what would be the best approach for this in the relational world?. And if a separate 'entity' table is the best option, then I guess I can use the following slice to create (and update?) records with linked tables: http://www.web2pyslices.com/main/slices/take_slice/102 Thanks for your recommendations. p.s. I have certainly already read the entire book :-) Carlos On Nov 17, 9:06 am, Ivan Matveev <imatvee...@gmail.com> wrote: > >> I have a 'central' table in my design called 'entity' > >> which contains lots of data (including names, company, emails, phones, > >> address, etc.) and I want many other tables to point to ONE entity > >> instance, i.e. 'entity' as an _extension_ of records in many different > >> tables. > > When you say 'joined tables' do you mean > SELECT tabl1.some_col, tabl2.other_col FROM tabl1 LEFT JOIN tabl2 ON ..... > or something else? > > I don't know a web2py component that can be used to edit a result of a > joined select. > > If your 'entity' table includes all fields you want to present to a > user you can avoid joins by use of references. I don't use db > references myself. I think usage can look like this: > > db.define_table('names', Field('name', 'string')) > db.define_table('companies', Field('company', 'string')) > > db.define_table('entity', > Field('name', db.names.name), > Field('company', db.companies.company)) > > also you can alter the way a field is represented with .represent and > .requires methods > > The details are in documentation on Database Abstraction > Layer(DAL)http://www.web2py.com/book/default/chapter/06 > > SQLFORM allows to edit a row in a table which is fine if you have all > fields in 'entity' table. > > If your 'entity' table contains references to rows in other tables you > will need SELECT...JOIN... > To edit its result you will have to make a page with multiple > SQLFORMs to edit individual rows in tables ' entity' refers to , or > make a custom form with SQLFORM.factory, or invent something. > > >> My background is with object databases, and this kind of design makes > >> sense, although I'm not sure if it makes sense with relation > >> databases?. > > It's pretty common to store an object information in a relation db as > a set of tables.
