Question

Please guide me if I’m on right track.

I’m trying to create database schema for Mobile Bill for a person X and how to define PK, FK for the table Bill_Detail_Lines.

Here are the assumptions:

1. Every customer will have a unique relationship number.
2. Bill_no will be unique as it is generated every month.
3. X can call to the same mobile no every month.
4. Account_no is associated with every mobile no and it doesn’t change.

Schema:

table: Bill_Headers

Relationship_no    - int, NOT NULL , PK
Bill_no            - int, NOT NULL , PK
Bill_date          - varchar(255), NOT NULL
Bill_charges       - int, NOT NULL

table: Bill_Detail_Lines

Account_no    - int, NOT NULL
Bill_no       - int, NOT NULL , FK
Relationship_no - int, NOT NULL, FK
Phone_no      - int, NOT NULL
Total_charges  - int

table: Customers

Relationship_no    - int, NOT NULL, PK
Customer_name      - varchar(255)
Address_line_1     - varchar(255) 
Address_line_2     - varchar(255) 
Address_line_3     - varchar(255) 
City               - varchar(255)
State              - varchar(255)
Country            - varchar(255)

Answer 1

I would recommend having a primary key for Bill_Detail_Lines. If each line represents a total of all calls made to a given number, then the natural PK seems to be (Relationship_no, Bill_no, Phone_no), or maybe (Relationship_no, Bill_no, Account_no).

If each line instead represents a single call, then I would probably add a Line_no column and make the PK (Relationship_no, Bill_no, Line_no).