SQLite with expo-sqlite in React Native - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ ui_behavior

intermediate

What is the output after inserting and querying a record?

Consider this React Native code using expo-sqlite. What will be the value of result.rows.length after the transaction?

React Native

import * as SQLite from 'expo-sqlite';
const db = SQLite.openDatabase('test.db');

// Create table and insert one record

db.transaction(tx => {
  tx.executeSql('CREATE TABLE IF NOT EXISTS items (id INTEGER PRIMARY KEY NOT NULL, name TEXT);');
  tx.executeSql('INSERT INTO items (name) VALUES (?);', ['apple']);
  tx.executeSql('SELECT * FROM items;', [], (_, result) => {
    console.log(result.rows.length);
  });
});

A Throws an error

B 1

C undefined

D 0

💡 Hint

Remember that the SELECT query runs after the INSERT in the same transaction.

The code creates a table if it doesn't exist, inserts one record, then queries all records. The SELECT callback receives the result with one row, so result.rows.length is 1.

❓ lifecycle

intermediate

When is the best time to open the SQLite database in a React Native app?

In a React Native app using expo-sqlite, when should you open the database connection to ensure it is ready for queries?

A Inside a useEffect hook with an empty dependency array

B Inside the component's render function

C Once, outside any component, at module load time

D Every time a button is pressed

💡 Hint

Opening the database multiple times can cause issues and is unnecessary.

Opening the database once at module load time ensures a single connection reused throughout the app. Opening inside render or on button press causes repeated openings and potential errors.

📝 Syntax

advanced

What error does this code produce?

What error will this code cause when running a transaction with expo-sqlite?

React Native

db.transaction(tx => {
  tx.executeSql('INSERT INTO items (name) VALUES (?);', ['banana'],
    () => console.log('Insert success'),
    () => { console.log('Insert failure'); return false; }
  );
});

A No error, logs 'Insert success' on success

B TypeError because the failure callback returns undefined instead of false

C SyntaxError due to missing parameters

D Runtime error because the failure callback does not return true

💡 Hint

The failure callback must return false to signal error handled.

The failure callback must return false to prevent the transaction from rolling back. Returning undefined causes a TypeError internally in expo-sqlite.

❓ navigation

advanced

How to ensure data is loaded before navigating?

You want to load data from SQLite before navigating to a new screen. Which approach ensures data is ready before navigation?

A Call navigation.navigate inside the executeSql success callback

B Call navigation.navigate immediately after starting the transaction

C Call navigation.navigate inside a setTimeout with 1 second delay

D Call navigation.navigate in a useEffect without dependencies

💡 Hint

SQLite queries are asynchronous; navigation must wait for completion.

The executeSql success callback runs after the query finishes. Navigating inside it ensures data is loaded before moving screens.

🧠 Conceptual

expert

Why use transactions in expo-sqlite?

Which is the main reason to use db.transaction when working with expo-sqlite?

A To encrypt the database contents for security

B To speed up queries by running them in parallel

C To automatically cache query results for offline use

D To execute multiple SQL statements atomically and rollback on failure

💡 Hint

Think about what happens if one statement fails inside a transaction.

Transactions ensure all statements succeed together or none apply, preserving data integrity. They do not speed up queries, cache results, or encrypt data.