Question

I am trying to implement a webservice that will take as input some ingredients, it will look up some recipies in a database and will return those ones that require all or some of the ingredients provided as input.

I can easily figure out the many to many relationship between the recipies and ingrdients so I am planning to have a table for recipies, one for ingredients and a link table in the middle. However, if I do this I am not sure how I can query the tables in an efficient way to get the information required.

To give an explicit example consider the following:

Input: Pasta, Chicken, Pesto, Tomatoes
Output should be:

• Pasta with Chicken in Tomato sauce (requiring Pasta, Chicken and tomatoes)
• Pasta with Pesto in the oven (requiring Pasta and Pesto)
• etc.

But output should not include Chicken with potatoes in tomato sause (since we do not have potatoes in the input ingredients).

I will be implementing this in Java and MySQL (although the Java part is probably not important for this question).

Can somebidy help me in approaching this. I am really after how to implement the Query but if you can think of other ways to approach it then these are welcome too.

Thanks in advance

Answer 1

First, put your list of ingredients that are “desired” into a temporary table. Let’s call this “desired”.

The following query will find recipes that have only ingredients in the desired table:

select r.recipe.name, group_concat(i.ingredientname separator ', ') as ingredients,
       count(*) as numingredients
from RecipeIngredient ri join
     Recipe r
     on ri.recipeid = r.recipeid join
     Ingredient i
     on ri.ingredientid = i.ingredientid left outer join
     Desired d
     on i.ingredientname = d.ingredientname
group by r.recipe.name
having max(case when d.ingredientname is null then 1 else 0 end) = 0 -- all ingredients in list