SQL(Left Join) 获取在另一个表中包含所有成分的所有食谱

Question

I need to get all recipes where all the ingredients are in another table and I don't know how I could to this.

'Ingredients' table (from the recipes):

1. Column is an ingredient id (unique)
2. Column is the recipe id for each ingredient
3. Column is the ingredient (at the moment string)

'UserIngredients' table (from the user):

1. Column is again just an id (unique)
2. Column is the ingredient

An example:

Ingredients table (of the recipes): User ingredients table:

Now I just want to get recipe id 13 back because this recipe just needs 'Butter' and 'Mehl'. What I don't want to get are the recipes which also need 'Butter' and 'Mehl' but also something else, because that's not in the user ingredients table.

Now I want a query(I think with an Inner Join) to get the recipes(ids) which have all ingredients in the other table. I hope you understand my problem and can help me. Big Thank You!

Answer 1

You need a LEFT join of ingredients to useringredients and then group by recipeid :

select i.recipeid
from ingredients i left join useringredients ui
on ui.ingredient = i.ingredient
group by i.recipeid
having count(*) = count(ui.ingredient)

The condition having count(*) = count(ui.ingredient) makes sure that all ingredients and no more are used for that recipeid