How to get data from a joined table

Question

I have two table joined with c.id = p.category_id. I want to get categories.name but it gives an error. Could anyone tell me how to get data from a joined table please?

function getGalleryone(){
     $data = array();
     $query = 'SELECT *
     FROM products AS p
     JOIN categories AS c
     ON c.id = p.category_id
     WHERE c.name = "Galleri1"
     AND p.status = "active"' ;
     $Q = $this->db->query($query);
     /*
     $this->db->select('*');
     $this->db->where('categories.name','Galleri 1');
     $this->db->where('products.status', 'active');
     $this->db->join('categories', 'categories.id = products.category_id');
     $this->db->order_by('name','random'); 
     $Q = $this->db->get('products');
     */
     if ($Q->num_rows() > 0){
       foreach ($Q->result_array() as $row){
         $data = array(
            "id" => $row['id'],
     "name" => $row['name'],
            "shortdesc" => $row['shortdesc'],
     ...
            ...
     "category" => $row['categories.name']
            );
       }
    }
    $Q->free_result();    
    return $data;

Database Products

CREATE TABLE IF NOT EXISTS `products` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(255) NOT NULL,
  `shortdesc` varchar(255) NOT NULL,
  `longdesc` text NOT NULL,
  `thumbnail` varchar(255) NOT NULL,
  `image` varchar(255) NOT NULL,
  `class` varchar(255) DEFAULT NULL,
  `grouping` varchar(16) DEFAULT NULL,
  `status` enum('active','inactive') NOT NULL,
  `category_id` int(11) NOT NULL,
  `featured` enum('true','false') NOT NULL,
  `price` float(4,2) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=MyISAM  DEFAULT CHARSET=latin1 AUTO_INCREMENT=20 ;

Database Categories

CREATE TABLE IF NOT EXISTS `categories` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(255) NOT NULL,
  `shortdesc` varchar(255) NOT NULL,
  `longdesc` text NOT NULL,
  `status` enum('active','inactive') NOT NULL,
  `parentid` int(11) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=MyISAM  DEFAULT CHARSET=latin1 AUTO_INCREMENT=15 ;
...
...

Error message

A PHP Error was encountered

Severity: Notice

Message: Undefined index: categories.name

Filename: models/mproducts.php

Line Number: 111

Thanks in advance.

Answer 1

Using * in the select you have 2 columns with the name "name". specify the * into the required columns rather (this will improve performance in any case) such as

c.name as categories_name

Answer 2

Because in your query you rename "categories" as "c"

Try changing:

"category" => $row['categories.name']

to

"category" => $row['c.name']

You shouldn't be using * either (as pointed out by someone else before I edited this) - that should have made it more obvious where the error was.

Answer 3

The categories.name column is actually going to be returned as just $row['name'] in the result set, not $row['categories.name']. Since products also has a name column, one is going to replace the other. Instead of selecting every field using the * wildcard, you should specify which fields you want returned. For example:

 SELECT p.*, c.name AS category
 FROM products AS p
 JOIN categories AS c
 ON c.id = p.category_id
 WHERE c.name = "Galleri1"
 AND p.status = "active"

Then you can reference the category name as $row['category'].