With the following assumptions I am trying to answer the nikels question ,

Accounts table is some thing like

Cretate table Accounts

(

acccountid int ,

cc_type     varchar(2) ,

……..

) 

and credit card table

create creditcard

(

accountid int ,

ccnumber varchar(50)

)

Here I am trying to use much under explored area of sub quires

Select  A.accountid,A.cc_type,

cc_no_or_dc_no 

=case when cc_type=’cc’ then 

( select cc_no from  creditcard B where A.accountid=B.accountid)

when cc_type=’dc’ then 

( select dc_no from debitcard B where A.accountid=B.accountid)

else ‘No more credit’	

end	

From 

Accounts A

I think this will solve his problem ,just for showing other credit methods are possible I added one more debitcard table ,This method will reduce no matches in the query

With best

Regards

John