Find all recipes with just vegan products - sql

Question

I have been trying to find all recipes with just vegan products but so far I just have this:
SELECT DISTINCT r.*
FROM recipes r INNER JOIN recipe_product rp ON r.id = rp.recipe_id
INNER JOIN products p ON rp.product_id = p.id
INNER JOIN product_specificdiet ps ON p.id = ps.product_id
INNER JOIN specificdiets sd ON ps.specific_diet_id = sd.id
WHERE sd.type = 'VEGAN';
But that query is giving me all the products that are vegan for all the recipes.
No idea how could I resolve it.
Thanks!

Answer 1

Two rules:
A product is vegan, if one of its specific diets is 'VEGAN'.
A recipe is vegan, if it only consists of vegan products.
In other words: A vegan recipe is a recipe for which NOT EXISTS any product that is NOT IN the set of vegan products.
select *
from recipes r
where not exists
(
select null -- non-vegan ingredient
from recipe_product rp
where rp.recipe_id = r.id
and rp.product_id not in
(
select ps.product_id -- vegan product
from product_specificdiet ps
join specificdiets sd ON ps.specific_diet_id = sd.id
where sd.type = 'VEGAN'
)
);

Answer 2

Use aggregation and a HAVING clause:
SELECT r.*
FROM recipes r JOIN
recipe_product rp
ON r.id = rp.recipe_id JOIN
products p
ON rp.product_id = p.id JOIN
product_specificdiet ps
ON p.id = ps.product_id JOIN
specificdiets sd
ON ps.specific_diet_id = sd.id
GROUP BY r.id
HAVING COUNT(*) FILTER (sd.type = 'VEGAN') = COUNT(*);
An alternative method would filter out ingredients that are not vegan and check for zero of them:
HAVING COUNT(*) FILTER (sd.type <> 'VEGAN') = 0;
Postgres is one of the databases that allows you to specify SELECT r.* even though you are only aggregating by r.id -- because that is allowed when the aggregation key is a primary key. In other databases, you may need to list the columns both in the SELECT and the GROUP BY if you want additional columns.

Answer 3

SELECT
re.*
FROM
recipes re
WHERE
re.id NOT IN (
SELECT
r.id
FROM
recipes r
LEFT JOIN
recipe_product rp ON r.id = rp.recipe_id
LEFT JOIN
products p ON rp.product_id = p.id
LEFT JOIN
product_specificdiet ps ON p.id = ps.product_id
LEFT JOIN
specificdiets sd ON ps.specific_diet_id = sd.id
WHERE
ISNULL(sd.type, '') != 'VEGAN';
)

Answer 4

Maybe by joining to a sub-query.
One that uses a filters the specific diets that only uses vegan types.
Untested notepad scribble :
SELECT r.*
FROM recipes r
JOIN
(
SELECT rp.recipe_id
FROM recipe_product rp
INNER JOIN products p
ON p.id = rp.product_id
INNER JOIN product_specificdiet ps
ON ps.product_id = p.id
LEFT JOIN specificdiets sd
ON sd.id = ps.specific_diet_id
GROUP BY rp.recipe_id
HAVING COUNT(CASE WHEN sd.type = 'VEGAN' THEN sd.id END) = COUNT(*)
) q
ON q.recipe_id = r.id;