Realm Subquery in React Native - react-native

Question

I'm new to realm. I have a schema like the following:
class MealItem {}
MealItem.schema = {
name: 'MealItem',
properties: {
mealId: {type: 'int'},
foodId: {type: 'int'},
},
};
I want to do the equivalent of :
SELECT
mealId
FROM MealItem
WHERE foodId = #food1
AND mealId IN (SELECT mealId FROM MealItem WHERE foodId = #food2
AND mealId IN (SELECT mealId FROM MealItem WHERE foodId = #food3))
I'm not sure where to begin other than to write A LOT of javascript for loops. Is there a less verbose way to do it?
more info
Basically I have two other objects like this:
class Meal {}
Meal.schema = {
name: 'Meal',
properties: {
mealId: {type: 'int'},
mealName: {type: 'string'},
},
};
class Food{}
Food.schema = {
name: 'Food',
properties: {
foodId: {type: 'int'},
foodName: {type: 'string'},
},
};
So my original query is meant to determine if given 3 different foods, does my restaurant offer a meal / combo for it.
For example, if you set food1 to Big Mac, food2 to Fries, food3 to Soft Drink, you should get a meal back called Big Mac Meal.
If you set food1 to Durian, food2 to Hot Pockets, food3 to Krusty Brand Imitation Gruel, no meal id will return, because my restaurant doesn't serve combo like that.

Answer 1

I don't know much about SQL but what I understand from your question is that you are trying to find meals that contains specific foods.
Realm queries and models works like a NoSQL database so you might need to think a little different while creating your models.
For example, lets say you have 3 tables. One contains Meals, one contains foods and one contains data about which MealId contains which FoodId. In Realm you don't need the 3 table. You can think as its a javascript object.
Example
const meal = {
mealId: 0001,
name: 'Big Fat Menu',
price: '4.99'
foods: [{
foodId: 11,
name: 'Burger'
}, {
foodId: 12,
name: 'Fries'
}, {
foodId: 13,
name: 'Coke'
}]
}
This javascript object can be modeled with Realm like this
const FoodSchema = {
name: 'Food',
primaryKey: 'foodId',
properties: {
foodId: 'string'
name: 'string',
}
};
const MealsSchema = {
name: 'Meal',
primaryKey: 'mealId',
properties: {
mealId: 'string'
name: 'string',
price: 'double',
foods: { type: 'list', , objectType: 'Food'}
}
};
With this schema you can make following query to get a meal that contains a specific food,
const meals = realm..objects('Meal').filtered(`foods.id == ${foodId}`)
This is just a small example to help you out a bit. Hope it helps.