Very common but...

I have one table named "Codes" where I put all the descriptions of the codes of my application. The key is a combination of 2 fields : code_KOI (kind of information) and code_Nr. So we have :

code_ID
code_KOI
code_Nr
code_Description

Now let say I have a table named "Users" :

user_ID
user_Name
user_AAA
user_BBB
user_CCC
...

The field user_AAA is linked to the table Codes with code_KOI = 1 and code_Nr = user_AAA, user_BBB is linked to the table Codes with code_KOI = 2 and code_Nr = user_BBB, user_CCC is linked to the table Codes with code_KOI = 3 and code_Nr = user_CCC...

Now I want to display the table Users in a datagrid, but of course I want the descriptions of the fields user_AAA, user_BBB, user_CCC,... instead of a number. So if user_AAA = 5, I want the description of code_KOI = 1 and code_Nr = 5.

How can I do this ?