Lets say I have the following 2 tables in a database:
[Movies] (Scheme: Automatic) ---------------------------- MovieID Name [Comments] (Scheme: Manual) ---------------------------- CommentID MovieID Text The ‘Movies’ table gets updated by a service every 10 minutes and the ‘Comments’ table gets updated manually by the users of the database.
Normally you’d just create a simple foreign-key relationship between the two tables with cascading updates and deletes but in this case I want to be able to keep the manually entered data even if the movie it refers to gets deleted (the update service isn’t that reliable). This should only be a problem in one-to-many releationships from an automatic table to a manual table. How would you separate the manual and the automatically populated parts of the database?
I was planning to add a foreign-key that isn’t maintaining referencial integrity and only cascades updates, not deletions. But are there any pitfalls I should be aware of by doing it this way? I mean, except the fact that I might end up with some of the manual data that doesn’t actually reference anything.
Edit / Clarification:
Just to clarify. The example tables are totally made up. In reality the DB will contain objects like servers, applications, application notes, versions numbers etc. Server related information will be populated automatically but some application details will be filled in manually. It could be information like special configurations and such. Even if the server record gets deleted the application notes on that server are still valuable and shouldn’t be deleted.
I’d suggest you use an import table that gets updated by the service and then populate the movies tables from that. Then you get to keep movies that are deleted in the movies table. Possible tagging them as deleted or obsolete, but you’d still be able to keep them for historical purposes.