what is much better design for combined primary keys?

First Design:
companycd, branchcd = always combined primary in all linked tables

..tblcompany.........tblbranch...........tblclient
....companycd.........companycd.........companycd
....companyname.....branchcd............branchcd
............................branchname........clie ntcd
.................................................. ..clientname

Second Design:
companybranchcd = primary in all linked tables (which is created in tblref)

..tblcompany.........tblbranch...........tblref.....................tblclient
....companycd.........companycd.........companycd. ............clientcd
....companyname.....branchcd............branchcd.. ..............companybranchcd
............................branchname........comp anybranchcd....clientname

I'm worrying about the performance of the two designs. The system can be use by different companies with different branches.

In first design, the combined primary (companycd, branchcd) is always linked to all tables in order to determine which company and branch as well.

In second design, the combined primary in first design was referenced to tblref in order to use only one primary (companybranchcd) in all linked tables that can also determine which company and branch as well by referencing to tblref.

Please share your vast knowledge. Thanks in advance.

the companybranchcd surrogate key does not need to be in a separate tblref table, it can be declared right in the tblbranch table

(by the way, you should learn to exclude the "tbl" prefix from your table names)

which is better? it's your choice

generally speaking, it all depends on the complexity of your application code

for example, if you get a client record in design two, you must do a join just to find out which company it belongs to, and this is not necessary if you're using natural keys

in addition, you have also to consider what you will do if you have clients that don't belong to a branch, just a company -- i.e. what will you do if you get a company that doesn't have branches? will you "invent" a "phony" branch just to fit the company into your design?

i added a field called type (headoffice or branch) in tblbranch. On that case, there is a company that has one branch (headoffice).

Thank you very much.