DB Design to store custom fields for a table
- by Fazal
Hi All, this question came up based on the responses I got for the question
http://stackoverflow.com/questions/2785033/getting-wierd-issue-with-to-number-function-in-oracle
As everyone suggested that storing Numeric values in VARCHAR2 columns is not a good practice (which I totally agree with), I am wondering about a basic Design choice our team has made and whether there are better way to design.
Problem Statement : We Have many tables where we want to give certain number of custom fields. The number of required custom fields is known, but what kind of attribute is mapped to the column is available to the user
E.g. I am putting down a hypothetical scenario below
Say you have a laptop which stores 50 attribute values for every laptop record. Each laptop attributes are created by the some admin who creates the laptop.
A user created a laptop product lets say lap1 with attributes String, String, numeric, numeric, String
Second user created laptop lap2 with attributes String,numeric,String,String,numeric
Currently there data in our design gets persisted as following
Laptop Table
Id Name field1 field2 field3 field4 field5
1 lap1 lappy lappy 12 13 lappy
2 lap2 lappy2 13 lappy2 lapp2 12
This example kind of simulates our requirement and our design
Now here if somebody is lookinup records for lap2 table doing a comparison on field2, We need to apply TO_NUMBER.
select * from laptop where name='lap2' and TO_NUMBER(field2) < 15
TO_NUMBER fails in some cases when query plan decides to first apply to_number instead of the other filter.
QUESTION
Is this a valid design?
What are the other alternative ways to solve this problem
One of our team mates suggested creating tables on the fly for such cases. Is that a good idea
How do popular ORM tools give custom fields or flex fields handling?
I hope I was able to make sense in the question.
Sorry for such a long text..
This causes us to use TO_NUMBER when queryio
