Question

I have created this database schema and with help from several users on here, I have a database which takes user submitted business entries stored in the business table, which are additionally grouped under one or several of about 10 catagories from the catagories table, in the tbl_works_catagories table by matching the bus_id to the catagory id.

For example, bus_id 21 could be associated with catagory_id 1, 2, 5, 7, 8.

CREATE TABLE `business` (
`bus_id` INT NOT NULL AUTO_INCREMENT, 
`bus_name` VARCHAR(50) NOT NULL, 
`bus_dscpn` TEXT NOT NULL, 
`bus_url` VARCHAR(255) NOT NULL,
PRIMARY KEY (`bus_id`)
)

CREATE TABLE `categories` (
`category_id` INT NOT NULL AUTO_INCREMENT, 
`category_name` VARCHAR(20) NOT NULL, 
PRIMARY KEY (`category_id`)
)

CREATE TABLE `tbl_works_categories` (
`bus_id` INT NOT NULL, 
`category_id` INT NOT NULL
)

Now, what i want to do next is a search function which will return businesses based on the catagory. For example, say one of the businesses entered into the business table is a bakers and when it was entered, it was catagorised under Food (catagory_id 1) and take-away (catagory_id 2).

So a visitor searches for businesses listed under the Food catagory, and is returned our friendly neighbourhood baker.

As with all PHP/MySQL, i just can’t (initially anyway) get my head around the logic, never mind the code!

Answer 1

You should setup foreign keys in your tables to link them together.

CREATE TABLE `business` (
`bus_id` INT NOT NULL AUTO_INCREMENT, 
`bus_name` VARCHAR(50) NOT NULL, 
`bus_dscpn` TEXT NOT NULL, 
`bus_url` VARCHAR(255) NOT NULL,
PRIMARY KEY (`bus_id`)
)

CREATE TABLE `categories` (
`category_id` INT NOT NULL AUTO_INCREMENT, 
`category_name` VARCHAR(20) NOT NULL, 
PRIMARY KEY (`category_id`)
)

CREATE TABLE `tbl_works_categories` (
`bus_id` INT NOT NULL, 
`category_id` INT NOT NULL,
FOREIGN KEY (`bus_id`) REFERENCES business(`bus_id`),
FOREIGN KEY (`category_id`) REFERENCES categories(`category_id`)
)

Then your search query would be something like:

SELECT b.*
FROM business b, categories c, tbl_works_categories t
WHERE 
   b.bus_id = t.bus_id AND
   c.category_id = t.category_id AND
   c.category_id = *SOME SEARCH VALUE*

which using JOIN would be written as:

SELECT b.*
FROM business b
  JOIN tbl_works_categories t
    ON b.bus_id = t.bus_id
  JOIN categories c
    ON c.category_id = t.category_id
WHERE c.category_id = *SOME SEARCH VALUE*