Steve Ngai (危 志 荣) KuaLa Lumpur, Malaysia

Hardcoded Values vs Lookup Tables

Hardcoded Values
You have a form, say, a registration form. In this form, you have these common fields, example Name, Age, Address, State, Country and etc. So, in your database design, how do you go about it? Create just one table to store all these fields? Something like below?

ID Name Age Address State Present_Country Country_Born
1 Steve 23 12-C-5 Wilayah Persekutuan Malaysia Singapore
2 Ngai 21 11-B-5 Selangor Malaysia Malaysia
3 Chee Weng 24 12-A-1 Pahang Malaysia Hong Kong

Now, consider these few questions:

  • In your add registration form, how do you populate those values to State, Present Country and Country Born? Because you just have one table, you have no choice but to hardcode those values.
  • What about edit registration form and view registration form page? How do you populate the values to State, Present Country and Country Born?
  • What happen when tomorrow government declare that Wilayah Persekutuan’s name has changed to KL Persekutuan?
  • To solve the above problems, you need to use an UPDATE query to change all records which has the value Wilayah Persekutuan to KL Persekutuan. Then you need to go to add registration form page to change the hardcoded value, as well as edit registration form and view registration form code. Maintenance nightmare!

    Lookup tables
    Let’s improve the design by having some lookup tables (the word “lookup” is my own term). First, we identify which fields we should have a lookup tables. I pick State, Present Country and Country Born. So, I need to create two lookup tables. Two because Present Country and Country Born can share the same table. Let’s have a simple design for these lookup tables.

    Both fields can just be varchar and below are some sample data

    State_Code State_Desc
    JH Johor
    KH Kedah
    KT Kelantan
    MK Melaka
    NS Negeri Sembilan
    PH Pahang
    PG Pulau Pinang
    PK Perak
    PS Perlis
    SB Sabah
    SW Sarawak
    SL Selangor
    TG Terengganu
    KL W.P. Kuala Lumpur
    LB W.P. Labuan
    PJ W.P. Putrajaya

    Country_Code Country_Desc
    CN China
    HK Hong Kong
    IN India
    MY Malaysia
    SG Singapore

    (View a complete country code)

    Right now, you can go back to your add registration form code, and you can use these look up tables to populate instead of using hardcoded values. You can use the State_Code and Country_Code as the value to store in user table, which becomes below,

    ID Name Age Address State Present_Country Country_Born
    1 Steve 23 12-C-5 KL MY SG
    2 Ngai 21 11-B-5 SL MY MY
    3 Chee Weng 24 12-A-1 PH MY HK

    You can also use these lookup tables to populate values for edit and view page.

    What happen when you realize that you are going to have a lot of lookup tables? Then, you can consider using just one resource table.