Question

For my website, I want to make something that works a bit like the tags on Stackoverflow – so some fields will have an autocompleter, and the autocompleter will display the number of times that other users have selected each suggested value. I suppose I’d have a database structure like this:

Articles
    ArticleID
    Content
    TagId

Tags
    TagId
    TagName
    Occurances

With the idea being that Occurances represents the number of times each TagId is referenced from the Articles table.

What is the best way to implement this? I could add/subtract from the occurances column on each of the stored procedures that update the article table, but I might miss one, and anyway, there is are some difficulties with this if a user removes a tag from something (as its easy to add 1 to the field for the newly added tag, but harder to work out which tag is being replaced.)

There is lots I don’t understand about sql-server. Is there a more robust way of counting occurances like this, that the database system will deal with itself? It would be ok if the data was cached once a day or something.

Answer 1

You could use this query to get the number of occurances by tag:

SELECT Tags.TagId, COUNT(Articles.TagId) as Occurances
  FROM Articles
  JOIN Tags ON Articles.TagId
  GROUP BY Tags.TagId

It could be used in a view or stored procedure, and you can set up your website’s cache to requery it as often as required.