Category and Sub-Categories with NodeJS and SQL Result - sql

Question

I am trying to build a JSON with NodeJS and SQL result.
The database is:
CREATE TABLE category (
id int(10) unsigned NOT NULL AUTO_INCREMENT,
title varchar(255) NOT NULL,
parent_id int(10) unsigned DEFAULT NULL,
PRIMARY KEY (id),
FOREIGN KEY (parent_id) REFERENCES category (id)
ON DELETE CASCADE ON UPDATE CASCADE
);
CREATE TABLE `items` (
`id` int unsigned NOT NULL AUTO_INCREMENT,
`cat_id` int unsigned DEFAULT NULL,
`parent_id` int unsigned DEFAULT NULL,
`name` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
PRIMARY KEY (`id`),
KEY `cat_id` (`cat_id`),
KEY `sub_id` (`parent_id`),
CONSTRAINT `cat_id` FOREIGN KEY (`cat_id`) REFERENCES `category` (`id`) ON DELETE CASCADE ON UPDATE CASCADE,
CONSTRAINT `sub_id` FOREIGN KEY (`parent_id`) REFERENCES `category` (`parent_id`) ON DELETE CASCADE ON UPDATE CASCADE
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8;
BEGIN;
INSERT INTO `category` VALUES (1, 'Colazione', NULL);
INSERT INTO `category` VALUES (2, 'Pranzo', NULL);
INSERT INTO `category` VALUES (3, 'Primi piatti', 2);
INSERT INTO `category` VALUES (4, 'Second dish', 2);
INSERT INTO `category` VALUES (5, 'Other things for lunch', 2);
COMMIT;
-- ----------------------------
-- Records of items
-- ----------------------------
BEGIN;
INSERT INTO `items` VALUES (1, 1, NULL, 'Cornetto');
INSERT INTO `items` VALUES (2, 3, 2, 'Pasta al sugo 1');
INSERT INTO `items` VALUES (3, 3, 2, 'Pasta al sugo 2');
INSERT INTO `items` VALUES (4, 3, 2, 'Pasta al sugo 3');
INSERT INTO `items` VALUES (5, 3, 2, 'Pasta al sugo 1 X');
INSERT INTO `items` VALUES (6, 3, 2, 'Pasta al sugo 2 X');
INSERT INTO `items` VALUES (7, 4, 2, 'Pasta al sugo 3 X');
COMMIT;
SET FOREIGN_KEY_CHECKS = 1;
The expected JSON is:
Category:
Sub-Categories:
Items:
If category doesn't got any sub-categories it will print:
Category:
Items:
We got more than one categories and each categories can have more than one sub-categories.
Each sub-categories can have more than one item.
How can I build a JSON result with NodeJS with SQL Query?
Expected JSON:
{
"menu": {
"categories": [
{
"id_category": 1,
"category_title": "Colazione",
"items": [
{
"id_item": 1,
"title": "Cornetto"
}
]
},
{
"id_category": 2,
"category_title": "Pranzo",
"subcategories": [
{
"title_subcategories": "Primi piatti",
"items": [
{
"id_item": 1,
"title": "Pasta al sugo 1"
},
{
"id_item": 2,
"title": "Pasta al sugo 2"
}
]
},
{
"title_subcategories": "Secondi piatti",
"items": [
{
"id_item": 1,
"title": "Pasta al sugo 3"
}
]
}
]
}
]
}
}

Answer 1

Here's what I came up with, although I haven't tested it:
async function buildJson(categories, items) {
// `query` is some function that queries the DB
const categries = await query('SELECT id AS id_category, title AS category_title, parent_id FROM categories');
const items = await query('SELECT id AS id_item, title AS item_title, cat_id FROM items');
const data = {
menu: {
categories: [],
},
};
const subcategories = categories.filter(category => category.parent_id !== null);
categories.filter(category => category.id_parent === null)
.forEach(category => {
data.menu.categories.push({
id_category: category.id_category,
category_title: category.category_title,
});
data.menu.categories.forEach(_category => {
_category.items = items.filter(item => item.cat_id === _category.id_category)
.map(item => ({
id_item: item.id_item,
title: item.title,
}));
_category.subcategories = categories.filter(__category => __category.parent_id === _category.id);
_category.subcategories.forEach(subcategory => {
subcategory.items = items.filter(item => item.cat_id === subcategory.id_category)
.map(item => ({
id_item: item.id_item,
title: item.title,
}));
});
});
});
return data;
}