Question

This is my current setup:
I have 2 tables, RECIPE and INGREDIENTS.
RECIPE holds the ID among other data. INGREDIENTS has X rows needed for each RECIPE.
How can one match 2 recipes with at least 2 matching ingredients?
I can do it specifying which ingredient must match, but my problem is when the recipe has more than 10 ingredients and I need two recipes that uses the same 2 ingredients, not knowing which ones.
Sorry my English, is not my natural language. I’ll post more details if needed, or if I wasn’t clear enough.

Pratical example:
Recipe 1 has: fish, potatoes and salt.
Recipe 2 has: turkey and rice.
Recipe 3 has: fish, rice and salt.
Recipe 4 has: turkey, potatoes and salt.

Result based on recipe 1 should be: 4
Result based on recipe 2 should be: None
Result based on recipe 3 should be: 1
Result based on recipe 4 should be: 1
(Yep, I need to run every recipe based on a filter not explained here)

Answer 1

Try something like this:

WITH REC_ING AS (
SELECT *
FROM RECIPE AS T1
INNER JOIN
INGREDIENTS AS T2
ON T1.ID = T2.ID)

SELECT *
FROM (
SELECT T1.ID AS ID1, T2.ID AS ID2
FROM REC_ING AS T1
INNER JOIN
REC_ING AS T2
ON T1.INGREDIENT_ID = T2.INGREDIENT_ID 
AND T1.ID != T2.ID) AS JOINED_TAB
GROUP BY ID1, ID2
HAVING COUNT(*) >= 2

This is a rough copy. If it sounds like what you’re looking for, I can make a more elaborate example (incl. SQL Fiddle).