I am trying to create a proper relationship on Hibernate and I have the following relationship between Recipe and Ingredients entities:

I thought that:

• One recipe can have multiple ingredients
• One ingredient can also be part of different recipes

In this situation, I would create many to many relationship.

However, by considering the unit and amount fields in the Ingredient entity, I think the amount of ingredient for a specific recipe may be changed later. In this situation, each ingredient should be belonging to a specific recipe. As a result, I create one to many relationship as shown on the image.

1. Is the approach (one to many) explained above true?

2. I also think that for a Category entity (that describes recipe categories e.g. vegetarian, diabetic, ...), I should use many to many relationship as the category is not identical for a specific recipe and when updating any category, all the related recipes should be affected. Is this true?

CodePudding user response：

If you want to map a many to many relationship, then you need a relationship table.

So your database tables will be

recipe <-> recipe_ingredient <-> ingredient

As you want to have attributes on the relationship amount and unit will then go to the recipe_ingredient table.

This will also result in three classes. Recipe, RecipeIngreident and Ingredient.

CodePudding user response：

The answer to both of your questions is yes. However, you should still consider many-to-many according to @Simon Martinelli's answer in this situation as you will eventually have many duplicate entries and data for Olive Oil across many different recipes which will only have unique IDs/Amounts/Units. However, this is just a suggestion and you are free to write your code however you wish.