Designer 2000, use of foreign keys
Date: 1997/10/02
Message-ID: <zwd2uAAO95M0Mwts_at_camk.demon.co.uk>#1/1
Hi,
[Quoted] I'm new to Designer 2000, so bear with me...
From a few days playing with this tool, I've come across what seems an oddity in the way it deals with foreign keys.
[Quoted] At the ERD level, the foreign key relationship is expressed as a relationship between tables with no reference to the attributes involved - the primary key is inferred.
[Quoted] [Quoted] At table level, after running the database wizard, D2K uses the ERD to [Quoted] determine that a foreign key is required and, therefore, a new column must be added to the created table to facilitate this. You end up with a new column called something like 'FE_FIRST_KEY'.
[Quoted] [Quoted] If you retrofit from a table to an entity (as you would after reverse engineering a database), D2K removes any column entries mentioned in the foreign keys. In this way it is consistent with the above, i.e ERD relationships do not have attributes.
This has some unfortunate consequences:
- At the entity creation level, you do not enter those attributes which
are foreign keys as the relationships will produce 'something'
attributes in their place.
-
[Quoted]
- How can you then reliably refer to these attributes which will only exist when you perform a database creation - which can/should only occur once and at quite a late stage?
- After reverse engineering a database, you cannot produce an ERD [Quoted] diagram which shows all the attributes associated with an entity - those relating to the foreign keys are removed.
- Is D2K not to be used for reverse engineering legacy systems?
- Is D2K not to be used where development using other tools occurs [Quoted] concurrently and entity attributes need to be known?
As you can tell, I'm totally confused by this tool.
I guess that what I'm asking is: 'Should the entity relationships include references to the key components?'
Please explain where I'm going wrong - I suspect that I'm thinking along implementation lines too early in the process.
Andy
-- Andy Hardy Senior IT Systems Engineer Cegelec AEG ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Opinions are mine and do not necessarily reflect those of Cegelec AEGReceived on Thu Oct 02 1997 - 00:00:00 CEST