codeigniter sql table conversion

Your base query might look like

SELECT MIN(id) id,
       MIN(location) location,
       product,
       MIN(CASE WHEN valuta = 'USD' THEN price END) price_usd,
       MIN(CASE WHEN valuta = 'JPY' THEN price END) price_jpy
  FROM product_price
 WHERE location = 'Boston'
 GROUP BY product
 ORDER BY id

Output:

| ID | LOCATION | PRODUCT | PRICE_USD | PRICE_JPY |
---------------------------------------------------
|  2 |   Boston |    milk |        19 |       180 |
|  4 |   Boston |   apple |       200 |    (null) |

Here is SQLFiddle demo

Now I'm not a codeigniter expert but in codeigniter it might look

$result = $this->db
               ->select(
                'MIN(id) id,
                 MIN(location) location,
                 product,
                 MIN(CASE WHEN valuta = 'USD' THEN price END) price_usd,
                 MIN(CASE WHEN valuta = 'JPY' THEN price END) price_jpy')
               ->from('product_price')
               ->where(array('location' => 'Boston')
               ->group_by(array('product')
               ->order_by(array('id')
               ->get();