sql query to determine the most similar goods by tags

Question

i\'m making an e-store, so i have 3 tables:

1) goods

id      | title
--------+----------- 
1       | Toy car
2       | Toy pony
3       | Do         


        

Answer 1

When you want to show the goods with goods id = 2

SELECT DISTINCT
  goods.*
FROM
  goods
  LEFT JOIN links ON links.goods_id = goods.id
WHERE links.tag_id IN (SELECT links.tag_id 
                       FROM links
                       WHERE links.goods_id = 2)

when you did not include goods_id = 2

SELECT DISTINCT
  goods.*
FROM
  goods
  LEFT JOIN links ON links.goods_id = goods.id
WHERE links.goods_id != 2 AND links.tag_id IN (SELECT links.tag_id 
                       FROM links
                       WHERE links.goods_id = 2)

can see on http://sqlfiddle.com/#!2/0fb60/38