Table with unknown number of columns

Question

We're in the process of designing a tiny database that will contain data regarding our software's usage. So in our programs/websites we will call a little service that logs some data regarding the session and the action performed. This way we can see what parts of our programs are heavily used, what the most common usage scenarios are etc.

The part I'm struggling with is how we are going to persist all the different kinds of actions. Because we don't know what exact actions and parameters all applications and future applications will be needing it is hard to decide on a data structure.

Currently it looks something like this:

   Actions
--------------
+ Id
+ ActionTypeId
+ SessionId
+ TimeStamp
+ Data01
+ Data02
+ Data03
...
+ Data10
+ DataBlob

I'm particularly doubtfull about all the datafields. In practice it will be either way to many columns or way too few. All concatenating them in one field will be hell to query on.

Have any suggestions?

Answer 1

Use another table, with

Data
---------
+ Value
+ ActionId

and then combine both tables, as in

select Value from Data, Action where Data.ActionId = Action.Id and ...