Retrieve single row as a query result for an EAV model in CodeIgniter

If you wish to reach your expected value, you have to use GROUP BY. For CodeIgniter you find it here, you find it Guide page in this part $this->db->group_by().

function getProductList() {
  return $this->db->select('p.name as product_name, concat(\'( \', GROUP_CONCAT(a.name), \' )\') as attribute_name, p.description as product_description')
                  ->from('products as p')
                  ->join('product_attributes as pa', 'pa.prod_id = p.id', 'LEFT')
                  ->join('attributes as a', 'a.id = pa.attr_id', 'LEFT')
                  ->group_by(array('p.name', 'p.description'))
                  ->get();
}

As you see here, grouping by the columns name i wish to print, and concat the column name you wish to retrieve. Hope this helps, Good luck.

EDITED

If you want to use concat or any of aggregation functions on more than one column, you have to do it as GROUP_CONCAT(a.name) as show below.

function getProductList() {
      return $this->db->select('p.name as product_name, 
                GROUP_CONCAT(a.name) as attribute_name, 
                GROUP_CONCAT(a.name) as attribute_name_2, 
                GROUP_CONCAT(a.name) as attribute_name_3, 
                p.description as product_description')
                  ->...
                  ->group_by(array('p.name', 'p.description'))
                  ->get();
}

Be aware, if you want to concat a column, you have not set it with group by statement.

These examples will give you a good idea about it, Good luck.

EDITED

This should work.

function getProductList() {
      return $this->db->select('p.name as product_name, 
                GROUP_CONCAT(a.name) as attribute_name, 
                p.description as product_description, 
                GROUP_CONCAT(d.name) as dimension_name, 
                GROUP_CONCAT(d.value) as dimension_value')
                  ->...
                  ->group_by(array('p.name', 'p.description'))
                  ->get();
}

EDITED

You could use distinct inside the group_concat so it gives a uniq data as you wish.

function getProductList() {
      return $this->db->select('p.name as product_name, 
                GROUP_CONCAT(DISTINCT a.name) as attribute_name, 
                p.description as product_description, 
                GROUP_CONCAT(DISTINCT d.name) as dimension_name, 
                GROUP_CONCAT(DISTINCT d.value) as dimension_value')
                  ->...
                  ->group_by(array('p.name', 'p.description'))
                  ->get();
}

EDITED

As i told you in the comments sections, you have to use subquery if you wish to do what you want, And this is how you can do it.

function getProductList() {
  return $this->db->select('pname, pdesc, aname, adesc, group_concat(dname), group_concat(dvalue)')
                  ->from('( select
                        p.name as pname,
                        p.description as pdesc,
                        GROUP_CONCAT(DISTINCT a.name) as aname,
                        GROUP_CONCAT(DISTINCT a.description) as adesc,
                        d.name as dname, 
                        d.value as dvalue

                        from products as p
                        left join product_attributes as pa on pa.product_id = p.id
                        left join attributes as a on a.id = pa.attribute_id
                        left join product_dimensions as pd on pd.product_id = p.id
                        left join dimensions as d on d.id = pd.dimension_id

                        group by p.id, p.description, d.name) as d' )
                  ->group_by(array('pname', 'pdesc', 'aname', 'adesc'))
                  ->get();
}

sql fiddle

I would just execute three simple queries. Get products. Get attributes. Get dimensions. Then map attributes and dimensions to corresponding products. This is how probably any ORM is performing eager loading.

I'm not familiar with codeigniter, but I think it should look something like this:

$query = $this->db->get('products');

$products = [];
foreach ($query->result() as $row) {
    // init empty arrays for attributes & dimensions
    $row->attributes = [];
    $row->dimensions = [];
    // should be indexed by id, so we can find id later to map attributes & dimensions
    $products[$row->id] = $row;
}

$attributes = $this->db
    ->select('pa.product_id, a.name')
    ->from('product_attributes as pa')
    ->join('attributes as a', 'a.id = pa.attribute_id')
    ->get();

$dimensions = $this->db
    ->select('pd.product_id, d.name, d.value')
    ->from('product_dimensions as pd')
    ->join('dimensions as d', 'd.id = pd.dimension_id')
    ->get();

foreach ($attributes as $attr) {
    $products[$attr->product_id]->attributes[] = $attr->name;
}

foreach ($dimensions as $dim) {
    $products[$dim->product_id]->dimensions[] = $dim;
    unset($dim->product_id);
}

Now you get all your data in a nicely nested structure. With echo json_encode($products, JSON_PRETTY_PRINT) you would get:

{
    "1": {
        "id": 1,
        "name": "Product_1",
        "description": "Lorem",
        "attributes": [
            "Attribute_1",
            "Attribute_2"
        ],
        "dimensions": [
            {
                "name": "length",
                "value": "15"
            },
            {
                "name": "breadth",
                "value": "25"
            },
            {
                "name": "height",
                "value": "15"
            }
        ]
    },
    "2": {
        "id": 2,
        "name": "Product_2",
        "description": "Ipsum",
        "attributes": [
            "Attribute_1",
            "Attribute_2",
            "Attribute_3"
        ],
        "dimensions": [
            {
                "name": "length",
                "value": "15"
            },
            {
                "name": "breadth",
                "value": "25"
            }
        ]
    }
}

You can traverse it in the view layer or your export code, and output in any way you need.

Update

In MySQL 5.7+ you can get the same result as a single JSON string with a single query:

select json_arrayagg(json_object(
  'id', p.id,
  'name', p.name,
  'description', p.description,
  'attributes', (
    select json_arrayagg(a.name)
    from product_attributes pa
    join attributes a on a.id = pa.attribute_id
    where pa.product_id = p.id
  ),
  'dimensions', ( 
    select json_arrayagg(json_object(
      'name',  d.name,
      'value', d.value
    ))
    from product_dimensions pd
    join dimensions d on d.id = pd.dimension_id
    where pd.product_id = p.id
  )
))
from products p;

db-fiddle

Or maybe you want something "simple" like this:

select p.*, (
    select group_concat(a.name order by a.id separator ', ')
    from product_attributes pa
    join attributes a on a.id = pa.attribute_id
    where pa.product_id = p.id
  ) as attributes, (
    select group_concat(d.name, ': ', d.value order by d.id separator ', ')
    from product_dimensions pd
    join dimensions d on d.id = pd.dimension_id
    where pd.product_id = p.id
  ) as dimensions
from products p;

which will return:

| id  | name      | description | attributes                            | dimensions                          |
| --- | --------- | ----------- | ------------------------------------- | ----------------------------------- |
| 1   | Product_1 | Lorem       | Attribute_1, Attribute_2              | length: 15, breadth: 25, height: 15 |
| 2   | Product_2 | Ipsum       | Attribute_1, Attribute_2, Attribute_3 | length: 15, breadth: 25             |

db-fiddle

But if you need the result exactly as in the question, then you can try this one:

select 
  p.name as product_name,
  (
    select concat('(', group_concat(a.name order by a.id separator ', '), ')')
    from product_attributes pa
    join attributes a on a.id = pa.attribute_id
    where pa.product_id = p.id
  ) as attribute_name,
  concat('(', group_concat(d.name order by d.id separator ', '), ')') as dimension_name,
  concat('(', group_concat(d.value order by d.id separator ', '), ')') as dimension_value,
  p.description as product_description
from products p
left join product_dimensions pd on pd.product_id = p.id
left join dimensions d on d.id = pd.dimension_id
group by p.id;

Result:

| product_name | product_description | attribute_name                          | dimension_name            | dimension_value |
| ------------ | ------------------- | --------------------------------------- | ------------------------- | --------------- |
| Product_1    | Lorem               | (Attribute_1, Attribute_2)              | (length, breadth, height) | (15, 25, 15)    |
| Product_2    | Ipsum               | (Attribute_1, Attribute_2, Attribute_3) | (length, breadth)         | (15, 25)        |

db-fiddle

you can use the MySQL function GROUP_CONCAT to get the desired result :

http://sqlfiddle.com/#!9/c51040/3

You will need to do it lile this

function getProductList() {
  return $this->db->select('p.name as product_name
                     , GROUP_CONCAT(a.name SEPARATOR ",") as attribute_name
                     , min(p.description) as product_description')
                  ->from('products as p')
                  ->join('product_attributes as pa', 'pa.prod_id = p.id', 'LEFT')
                  ->join('attributes as a', 'a.id = pa.attr_id', 'LEFT')
                  ->group_by("p.name");
                  ->get();
}

Try This using Sub Query. Codeigniter Code :

$this->db->select("select p.name as pname, p.description as pdesc, t2.aname, t2.adesc,t3.dname,t3.dvalue");
$this->db->from("products p");
$this->db->join("(select pa.product_id,GROUP_CONCAT(a.name) as aname, GROUP_CONCAT(a.description) as adesc from  product_attributes as pa 
left join attributes as a on a.id = pa.attribute_id
group by pa.product_id) t2","t2.product_id=p.id","left");
$this->db->join("(select group_concat(name) as dname,group_concat(value) as dvalue,pd.product_id from product_dimensions pd
left join dimensions d on d.id = pd.dimension_id
group by pd.product_id) t3","t3 on t3.product_id = p.id","left");
$this->db->group_by("p.id");
$this->db->get()->result_array();

MySql Query :

select p.name as pname, p.description as pdesc, t2.aname, t2.adesc,t3.dname,t3.dvalue
from products as p
left join (select pa.product_id,GROUP_CONCAT(a.name) as aname, GROUP_CONCAT(a.description) as adesc from  product_attributes as pa 
left join attributes as a on a.id = pa.attribute_id
group by pa.product_id) t2 on t2.product_id=p.id
left join
(select group_concat(name) as dname,group_concat(value) as dvalue,pd.product_id from product_dimensions pd
left join dimensions d on d.id = pd.dimension_id
group by pd.product_id) t3 on t3.product_id = p.id
group by p.id

Click here to see result