Database – Should I ever DELETE (SQL and DB) anything

databasesql

I am curious, should I ever delete anything? Right now I am building a site (for myself) which allows you to subscribe to users which you then receive a message every time the user has upload content.

Or comments, if there is a thread and someone writes a direct comment to your comment you get a message saying so. Should I ever delete those or just simply hide it?

Each subscription has three (64bit) int. id, commentId, recipientId. You can find out who wrote to you looking at the comment table via commentId. If i dont use delete it will have a 4th int saying the status (show, hidden/delete).

Should I leave them or delete them? If I should delete them, then why? I can see maybe when there is personal user that you must delete on request but other then that should I ever delete?

I don't know which SQL DB I'll be using.

-edit-

Thanks guys. Right now I'll delete nothing except for things i can generate. Such as that subscription thing about.

Best Answer

The company I work for offers software to people in certain regulated industries so generally I have the "never delete anything" attitude because if you delete anything you have lost the completeness of your audit trail. Instead mark the information as deleted (or move it to an archive version of the tables) and record who "deleted" it and when.

The only reasons to really delete stuff are

  • if you are running out of space (but disk is cheap these days)
  • for efficiency (but if your data structure is well indexed and not badly fragmented this will make little difference)
  • for legal reasons (if you are asked to remove someone's details you will most likely have to comply, depending on local data protection laws, or if the content itself infringes some law)

Your users may be thankful of nothing getting really deleted, if they accidentally delete something useful and you can get it back. And if an upset user who has previously provided valuable information to the site throws a hissy fit and deletes all their posts in vengeance you can retract the deletions easily.

One extra very important point: you shuold make it clear in your terms of service that information may not be really deleted when the user can not see it any more, and provide a route (if only "email x@x.x and ask for it to be done") for them to really delete data they have the right under relevant laws to ask to be deleted.

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