如何比较数据库中的整数列表？ 爪哇

Question

We have entity:

Class Drink {
Long id;
String name;
List "Integer" ingredients; // We store ingredient's numbers in this list
}

For example: id = 1, name = Mojito, ingredients = {5,7,3,8}

Let's say, i want to find a drink based on ingredients. How should I do that?

1. Retrieve all cocktails from data base and iterate through them for comparison?
2. Or comparison should be conducted in a data-base? If this is correct answer, How can I to that? (How to compare Lists of Integers in the DB)?

Answer 1

Most likely you'll want to filter the data on the database level. The exact solution depends on the type of the database structure and the framework that you use, but since you use PostgreSQL, I assume you have a relational database structure, and since you speak of an "entity", I assume you use something like Hibernate or JPA to interact with it.

Then probably your drinks should reference their ingredients not as numbers, but as entities. This is how the mapping could look like:

class Drink {

    Long id;

    String name;

    @ManyToMany
    @JoinTable(tableName = "drink_ingredients")
    List<Ingredient> ingredients;
}

class Ingredient {

    Long id;

    String name;
}

Then a query to find all drinks containing a specific ingredient would be:

Query query = entityManager.createQuery("select d from Drink d " 
    + "join d.ingredients i "
    + "where i.name = :ingredientName");
query.setParameter("ingredientName", "Lime");
List<Drink> drinks = (List<Drink>) query.getResultList();