Question

I am wanting to allow users to tag items so that they can search for them using tags. What is the best way of achieving this cleanly? So far the solution I have come up with only involves adding two extra tables to my current db system.

<db Trackable product 1>
int id;
info etc
</>

<db Trackable product 2>
int id;
info etc
</>

//defines the M:M relationship between Tag and various types of Trackable products
<db TagLink>
int trackableProd1Id
int trackableProd2Id
int tagId
</>

<db Tag>
int tagId
tag name etc
</>

Is this a good way to go about it? A benefit of this approach is that it should scale well and it also allows me to add more trackable products in the future by simply adding a column to TagLink table. This is obviously not a good idea if I planned to track 10’s of tables but for up to 3-4 tables it should prove to work well shouldn’t it?

Answer 1

Rather than multiple “TrackableProd_N_id” columns in TagLink table, I suggest you introduce a multi-column foreign key, such as

   TagLink table
      int ProdGroup    -- "points" to table 1 vs. table 2 etc.
      int ProductId
      int TagId

in this fashion when additional sources of product come up you merely need to “invent” a new ProdGroup number for them, and use the ProductId (or other primary key from said table).