Re: Designer 2000, use of foreign keys

[Quoted] Des2k ERD is for "conceptual" modelling, and a key part of this is that attributes are not need or used for relationships. This by design and intent.

You really want to use the "Data Schema" diagrammer for working with actual database/table/column design.

Andy Hardy <Andy_Hardy_at_camk.demon.co.uk> wrote:

>Hi,
>
>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.
>
>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.
>
>At table level, after running the database wizard, D2K uses the ERD to
>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'.
>
>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:
>
>1. 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.
>
>a) 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?
>
>2. After reverse engineering a database, you cannot produce an ERD
>diagram which shows all the attributes associated with an entity - those
>relating to the foreign keys are removed.
>
>a) How can you produce 'database' documentation in which a percentage of
>the columns/attributes will not be displayed?
>
>b) Having reverse engineered a database and related forms, how could
>they possibly re-generate correctly again when some of the attributes
>are now missing?
>
>3. Is D2K not to be used for reverse engineering legacy systems?
>
>4. Is D2K not to be used where development using other tools occurs
>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

-JJ

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Don't miss the Oracle Development Tools User Group Conference in St. Louis, Nov. 2-5. See http://www.odtug.com for more information. Received on Thu Oct 02 1997 - 00:00:00 CEST