Database structure for a classifieds website

Question

I am developing a classifieds website similar to Quickr.com.

The main problem is that each category requires a different set of properties. For example, for a mobile phone the attributes might be Manufacturer, Operating System, Is Touch Screen, Is 3G enabled etc... Whereas for an apartment the attributes are Number of bedrooms, Is furnished, Which floor, total area etc. Since the attributes and the number of attributes varies for each category, I am keeping the attributes and their values in separate tables.

My current database structure is

Table classifieds_ads

This table stores all the ads. One record per ad.

ad_id
ad_title
ad_desc
ad_created_on
cat_id

Sample data

-----------------------------------------------------------------------------------------------
|ad_id | ad_title    | ad_desc                                       | ad_created_on | cat_id |
-----------------------------------------------------------------------------------------------
|1     | Nokia Phone | Nokia n97 phone for sale. Excellent condition | <timestamp>   | 2      |
-----------------------------------------------------------------------------------------------

Table classifieds_cat

This table stores all the available category. cat_id in classifieds_ads table relates to cat_id in this table.

cat_id
category
parent_cid

Sample data

-------------------------------------------
|cat_id| category            | parent_cid |
-------------------------------------------
|1     | Electronics         | NULL       |
|2     | Mobile Phone        | 1          |
|3     | Apartments          | NULL       |
|4     | Apartments - Sale   | 3          |
-------------------------------------------

Table classifieds_attribute

This table contains all the available attributes for a particular category. Relates to classifieds_cat table.

attr_id
cat_id
input_type
attr_label
attr_name

Sample data

-----------------------------------------------------------
|attr_id | cat_id | attr_label       | attr_name          |
-----------------------------------------------------------
|1       | 2      | Operating System | Operating_System   |
|2       | 2      | Is Touch Screen  | Touch_Screen       |
|3       | 2      | Manufacturer     | Manufacturer       |
|4       | 3      | Bedrooms         | Bedrooms           |
|5       | 3      | Total Area       | Area               |
|6       | 3      | Posted By        | Posted_By          |
-----------------------------------------------------------

Table classifieds_attr_value

This table stores the attribute value for each ad in classifieds_ads table.

attr_val_id attr_id ad_id attr_val

Sample data

---------------------------------------------
|attr_val_id | attr_id | ad_id | attr_val   |
---------------------------------------------
|1           | 1       | 1     | Symbian OS |
|2           | 2       | 1     | 1          |
|3           | 3       | 1     | Nokia      |
---------------------------------------------

========

• Is this design okay?
• Is it possible to index this data with solr?
• How can I perform a faceted search on this data?
• Does MySQL support field collapsing like solr?

Answer 1

My suggestion is to remove cat_id from the classifieds_attribute table, then create a new table.

The new table would look like:

cat_attr | id | cat_id | attr_id

This should help you decrease redundancy.