Question

I have the following database, the first table users is a table containing my users, userid is a primary key.

The next is my results table, now for each user, there can be a result with an id and it can be against an exam. Is it ok in this scenario to use “id” as a primary key and “userid” as a foreign key? Is there a better way I could model this scenario?

These then link to the corresponding exams…

Answer 1

I would probably not have userid as a varchar. I would have that as an int as well.

So the user table is like this:

userId int
userName varchar
firstName varchar
lastName varchar

And then the forenkey in the results table table would be an int. Like this:

userId int
result varchar
id int
examid INT

Becuase if you are plaing on JOIN ing the tables together then JOIN ing on a varchar is not as fast as JOIN ing on a INT

EDIT

That depend on how much data you are planing to store. Beause you know that there is a minimum chans that GUIDs are not unique. Simple proof that GUID is not unique. I think if I would design this database I would go with an int. Becuase it feels a little bit overkill to use a GUID as a userid