Question

I want to begin by stating I’m an SQL noob, so I’d appreciate any suggestions or comments on my workflow and/or mindset when trying to solve this issue.

What I’m doing is gathering usage statistics about several applications, in several categories (not all categories necessarily apply to all applications), storing them in a database.

I’ve set up a few tables to do that, and then one table to link everything together that’s structured like so (from now on: Dtable):

(column name - details)  
UserID  - foreign key to another table which stores users data  
ApplicationID - foreign key to another table which stores applications data  
CategoryID - foreign key to another table which holds a list of different categories  
Value - the actual data

Each application gathers the data, then submits it to the database using a stored procedure. As the amount of data can be different based on actual usage (not always sending every category) and for each application, I was thinking of sending the data as a DataTable with a list of CategoryID and Value so I won’t have to call a procedure for every individual category (Ptable).

I need to update each record in Dtable to the correct value in Ptable according to CategoryID, but also filtered by UserID and ApplicationID. UserID and ApplicationID will be given as two other parameters to the Stored Procedure. Ptable only contains a list of CategoryID / Value records.

Now, I read about Cursors (for each record in the table parameter set the relevant data in the database table), but the consensus seems to be “Avoid at all costs”.

How would I go about updating the table, then, based on the varying records in Ptable?

P.S.
The tables are structured like so to keep agility and scalability in adding more categories/applications in the future. If there’s a better way to do it I’ll be happy to know.

Answer 1

I believe the update statement would look something like this, where @ApplicationID and @UserID are the stored proc’s other parameters:

update Dtable
    set Dtable.Value = p.Value
    from Ptable p
    where Dtable.UserID = @UserID
        and Dtable.ApplicationID = @ApplicationID
        and Dtable.CategoryID = p.CategoryID;