Need explode like function in MySql? You can do it using RegExp.

Working with a client I had a requirement where a product may belong to multiple categories. Now you can do it by either creating a separate table showing the relation between the two, or you can simply add a new field in the product table and save all the respective categories in a comma separated form.

The problem with the second solution is that you can’t really write a SQL query to retrieve products belonging to a specific category! As there is no php function like explode to do the job for you. Here is an example..

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CREATE TABLE `rbp_products` (
     `id` INT(11) NOT NULL AUTO_INCREMENT,
     `name` VARCHAR(255) DEFAULT NULL,
     `image` VARCHAR(55) DEFAULT NULL,
     `description` text,
     `category` text,
     `created` datetime DEFAULT NULL,
     PRIMARY KEY  (`id`)
)
 
INSERT  INTO `rbp_products`(`id`,`name`,`image`,`description`,`category`,`created`) VALUES 
       (1,'test first1234','625301270541172.jpg','Test product description..\r\nTest product description..','1,3,5,8,15,17,25','2010-04-04 07:40:32'),
       (2,'another test1','266381270541206.jpg','another product description..\r\n\r\nanother product description..','1,2,4,6,10,11,18,24,26','2010-04-04 07:41:52'),
       (3,'Sports One','514641270366953.jpg','Sports One test product..','2,4,8,9,11,15,19,24','2010-04-04 07:42:35');

Now I want to search all products belonging to category 11..

suppose $cat_id = 11;

we can try this..

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SELECT * FROM rbp_products WHERE '{$cat_id}' IN (category)

it looks ok if it was replaced by the category list related to that product which would make it like this for product ID ’1′..

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SELECT * FROM rbp_products WHERE '{$cat_id}' IN (1,3,5,8,15,17,25)

But it would not work because the expr needs a list of values and we have just issued the category string which obviously is not a list. Since we don’t have explode in MySql we can’t convert it to a list as we do in PHP all the time..

fortunately MySql supports RegExp which is a very strong tool when it comes to string manipulation. We can do it using RegExp, here is how..

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SELECT DISTINCT * FROM rbp_products WHERE category REGEXP '($cat_id,)|$cat_id$'

so the query would be

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SELECT DISTINCT * FROM rbp_products WHERE category REGEXP '(11,)|11$'

this means fetch all different products related to category contains ’11,’ or contains only 11 at the end of string i.e. if 11 is not the end of string it must have a comma followed it.

So you can now retrieve all the records related to any specific category easily