Question

I have a table called ‘notes’, on this table I need to track who made that note, but the problem is that the creator of the note can be a user stored in one of three possible tables:

users
leads
managers

I have though of simply create three fields on ‘notes’ to represent the three possible relations: note.user, note.lead, note.manager

With this approach I would be forced to create three table joins when requesting the notes to gather the creators information, and I don’t think that is the way to go, so I would like to hear your ideas or comments and what would be the best approach on this.

Answer 1

For me personally this smells like a design problem on a totally different part of the schema: Are manageers not users? Do leads carry person information?

With any approach that creates a relation between one column and one of three others, you will need three joins for the select. If you can’t rectify the underlying problem, I recommend you use

note_type ENUM('users','leads','managers')

as an additional field and

SELECT
  ...
  IFNULL(users.name(IFNULL(managers.name,leads.name))) AS name
  ..
FROM notes
LEFT JOIN users ON notes.note_type='users' AND users.id=notes.note_source
LEFT JOIN managers ON notes.note_type='managers' AND managers.id=notes.note_source
LEFT JOIN leads ON notes.note_type='leads' AND leads.id=notes.note_source
...

for the query