sql architect regarding one to many relationship between table I have theoretical question. 

I have two tables. as follows:

Table A

--------------------------
 id | name | type  | bid |
--------------------------
 1  |  x   | round | 1   |
--------------------------
 2  |  y   | square| 1   |
--------------------------


bid is foreign key to table B. Table A to Table B is one to many relationship.

Table B

-----------------------------
 id | home_zip | office_zip |
-----------------------------
 1  |  6993    | 6666       |
-----------------------------
 2  |  5867    | 6993       |
-----------------------------


I am doing search and finding information on home_zip and office_zip column and dumping into another table C. Table B to table C is many to one relationship

Table C

------------------------
 id | zip | information|
------------------------
 1  | 6993| 66668      |
------------------------
 2  | 6666| 98237      |
------------------------


My question:

Is it is good to add column b.id in table C, and create duplicated record? or don't include b.id in table C.
I would just add b.id into table C and avoid columns [zip] and [information] at all because you can easily find [zip] and [information] by joining table B via b.id (which is a PK)