Local Storage in Flutter: SQLite and Hive

The local storage is saving structured data inside the user’s device.

SharedPreferences is like a sticky note: great for jotting down a phone number, terrible for writing a novel.

If your App needs:

• Save thousands of records.
• Perform complex searches (e.g., “Users over 18 living in Madrid”).
• Relate data (Orders belonging to a Customer).

You need a database. In Flutter, we can choose between relational solutions, key-value stores, and object-oriented databases. Let’s compare two well-known approaches.

SQLite and Relational Databases

SQLite is the mobile industry standard. Android and iOS come with it pre-installed. It is a Relational (SQL) database.

In Flutter, we use the sqflite package.

How does it work?

Think of Excel spreadsheets (Tables) that relate to each other. You have to define a strict schema (CREATE TABLE…) and write queries in SQL language.

// Conceptual example of sqflite
// 1. Write raw SQL (Prone to syntax errors)
await db.execute(
  'CREATE TABLE Test (id INTEGER PRIMARY KEY, name TEXT, value INTEGER, num REAL)'
);

// 2. Insert maps
await db.insert('Test', {'name': 'my name', 'value': 123});

// 3. Query
List<Map> list = await db.rawQuery('SELECT * FROM Test WHERE value > ?', [100]);

Hive as a Key-Value Store

Hive is a NoSQL key-value store written in Dart. Its API resembles a persistent Map and is convenient for data queried by key.

How does it work?

Think of a “Box”. Inside the box, you can put whatever you want, assigning it a key. It’s like a persistent and supercharged Map<String, dynamic>.

// Conceptual example of Hive
// 1. Open a box
var box = await Hive.openBox('testBox');

// 2. Save data (Looks like a Map)
await box.put('name', 'David');
await box.put('friends', ['Ana', 'Juan', 'Pedro']); // Saves lists directly

// 3. Read
var name = box.get('name');