Question

How to SELECT 3 table in one query and show all product with price?

Below is my database structure(MySql) :

categories

+-------------+------------+
 category_id  | parent_id  |
+-------------+------------+
  1           |      0     
  2           |      1
  3           |      1
  4           |      1
  5           |      2
  6           |      3

products_to_categories

+-------------+------------+
 product_id   | category_id|
+-------------+------------+
  54          |      0     
  55          |      2
  56          |      2
  57          |      2
  58          |      3
  59          |      3
  60          |      4

products

+-------------+------------+
 product_id   |    price   |
+-------------+------------+
  54          |      10.50     
  55          |      11.20
  56          |      1.00
  57          |      22.20
  58          |      32.0
  59          |      32.0
  60          |      22.0

Below is my condition ;

1. table categories : parent_id = '1'  
(result : 2,3,4)

2. table products_to_categories : category_id = result categories(result : 2,3,4) 
(result : 55,56,57,58,59,60)

3. table products : inner join or left join table product to display price where product_id = result products_to_categories(result : 55,56,57,58,59,60)

Final Output

  55 - 11.20
  56 - 1.00
  57 - 22.20
  58 - 32.0
  59 - 32.0
  60 - 22.0

Before i post this question here is my previous query(im stuck how to proceed to condition 2)

$sql_all = mysql_query("SELECT cat.parent_id,cat.category_id FROM categories cat WHERE cat.parent_id='1' ");
while($row = mysql_fetch_array($sql_all)) {
echo $row['categories_id'].'<br/>'; 
}

thanks.

Answer 1

Try this,

SELECT  c.*
FROM    categories a
        INNER JOIN products_to_categories b
            ON a.category_id = b.category_id
        INNER JOIN products c
            ON b.product_id = c.product_id
WHERE  a.parent_id = 1

This will display all records from products table having parent_id = 1.