Compound queries (multiple where) in Firebase - Mini Project: Build & Apply

Compound queries (multiple where) in Firebase

📖 Scenario: You are managing a Firebase Firestore database for a small online bookstore. You want to find books that meet multiple conditions to help customers find the right books quickly.

🎯 Goal: Build a Firebase Firestore query that uses multiple where clauses to filter books by genre and price.

📋 What You'll Learn

Create a collection reference to books

Add a configuration variable for the maximum price filter

Write a compound query using two where clauses: one for genre and one for price

Complete the query by calling getDocs() to retrieve the filtered books

💡 Why This Matters

🌍 Real World

Filtering data with multiple conditions is common in apps like online stores, where users want to find items matching several criteria.

💼 Career

Understanding compound queries in Firestore is essential for backend and full-stack developers working with Firebase to build efficient and user-friendly applications.

1

Create a collection reference to books

Create a variable called booksRef that references the Firestore collection named books using collection(db, 'books').

Firebase

import { collection, query, where, getDocs } from 'firebase/firestore';
import { db } from './firebaseConfig';

// Create a collection reference to 'books'
// Your code here

Need a hint?

Use the collection function with db and the string 'books'.

2

Add a configuration variable for the maximum price filter

Create a constant called maxPrice and set it to 20 to filter books priced at $20 or less.

Firebase

import { collection, query, where, getDocs } from 'firebase/firestore';
import { db } from './firebaseConfig';

const booksRef = collection(db, 'books');

// Set maxPrice to 20
// Your code here

Need a hint?

Use const maxPrice = 20; to set the price limit.

3

Write a compound query using two where clauses

Create a variable called booksQuery that uses query() with booksRef and two where clauses: one where genre equals 'fiction', and another where price is less than or equal to maxPrice.

Firebase

import { collection, query, where, getDocs } from 'firebase/firestore';
import { db } from './firebaseConfig';

const booksRef = collection(db, 'books');
const maxPrice = 20;

// Create a compound query filtering genre and price
// Your code here

Need a hint?

Use query() with where filters for genre and price.

4

Complete the query by calling getDocs()

Create an async function called fetchBooks that calls getDocs(booksQuery) and stores the result in a variable called querySnapshot.

Firebase

import { collection, query, where, getDocs } from 'firebase/firestore';
import { db } from './firebaseConfig';

const booksRef = collection(db, 'books');
const maxPrice = 20;

const booksQuery = query(booksRef, where('genre', '==', 'fiction'), where('price', '<=', maxPrice));

// Create async function fetchBooks to get documents
// Your code here

Need a hint?

Define an async function and use await getDocs(booksQuery) inside it.