Question

I find my self lost while trying to create an actually pretty easy SQL statement.

I got a database with 3 Tables:

• recipes – storing some recipes names for cooking
• ingredients_recipes – links ingredients with recipes
• ingredients – the ingredients used by recipes.

its stored like this to make it double-clear:

recipes:

id | name
 1 | lasagne alla bolognese
 2 | tuna with tomatoes

ingredients:

id | name
 1 | lasagne slices
 2 | meat
 3 | tomato
 4 | tuna

and join-table ingredients_recipes:

ingredient_id | recipes_id
            1 | 1
            2 | 1
            3 | 1
            3 | 2
            4 | 2 

So as you can see, there are 2 really undelicios recipes which I should at least give some spices. But what I want to do before is selecting recipes by ingredients.

I want to have all my recipes having meat AND tomatoes:

SELECT recipes.name FROM recipes r
INNER JOIN ingredients_recipes ir ON ir.recipes_id = r.id
WHERE ir.ingredient_id IN ( 2 ) AND ir.ingredient_id IN ( 3 )

-> lasagna.. fine! (I use IN since there might be a bunch of ingredients, like “tomato”, “tomatoes”, “tomatoes, sliced” etc.. )

When I want to have e.g. all recipes having tomatoes but NOT having tuna, I tried:

SELECT recipes.name FROM recipes r
INNER JOIN ingredients_recipes ir ON ir.recipes_id = r.id
WHERE ir.ingredient_id IN ( 2 ) AND ir.ingredient_id NOT IN ( 4 )

-> still getting tuna – since one of the rows i join does not contain ingredient 4. okay :/

What I am wondering now is, what do I have to do, to get my desired results.
I currently put an arrow to my knee by doing a subselect like this:

SELECT recipes.name FROM recipes r
INNER JOIN ingredients_recipes ir ON ir.recipes_id = r.id
WHERE (
        ir.ingredient_id IN ( 2 ) -- or more..
        AND 
        recipes.id NOT IN ( SELECT recipes_id FROM ingredients_recipes
                             WHERE ingredient_id IN ( 4 ) -- actually i paste names of the ingredients.. but that is not the case. just to shorten the query.. by filling in a comment twice as long..
                            )
      )

as I am quite new to mySQL, I don’t even know what to google for. so any help in that case, and o/c the better SQL statement would be ..

 IN(awesome).

Edit: ah, and yes I actually do grouping.. 😉

Answer 1

This is one way. (untested)

SELECT r.name 
FROM recipes r
JOIN ingredients_recipes ir 
  ON ir.recipe_id = r.id
WHERE EXISTS ( SELECT *
    FROM ingredients_recipes ex
    WHERE ex.recipe_id = r.recipe_id
    AND ex.ingredient_id IN ( 2 , 3 )
    GROUP BY nx.recipe_id
    HAVING COUNT(*) = 2
    );

The only way for count(*) to be 2 is if 2 and 3 ar both present.

Another way could be: (still untested)

SELECT r.name 
FROM recipes r
JOIN ingredients_recipes ir 
  ON ir.recipe_id = r.id
WHERE EXISTS ( SELECT *
    FROM ingredients_recipes ex
    WHERE ex.recipe_id = r.recipe_id
    AND ex.ingredient_id = 2
    )
AND EXISTS ( SELECT *
    FROM ingredients_recipes ex
    WHERE ex.recipe_id = r.recipe_id
    AND ex.ingredient_id = 3
    );

UPDATE: (i had misread the question) If you also don’t want recipes with particular ingredients present you could add yet another subquery “leg” to the query:

... AND NOT EXISTS ( SELECT *
    FROM ingredients_recipes ex
    WHERE ex.recipe_id = r.recipe_id
    AND ex.ingredient_id IN ( 4,5 )
    );