ORM concept (Sequelize, Prisma overview) in Node.js - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

What does ORM stand for and what is its main purpose?

Choose the correct definition and purpose of ORM in Node.js frameworks like Sequelize and Prisma.

A Object Reactive Model; it creates reactive objects for UI updates.

B Online Resource Manager; it manages online resources like APIs and external services.

C Operational Runtime Middleware; it handles middleware operations during runtime.

D Object-Relational Mapping; it helps convert data between incompatible systems by mapping objects in code to database tables.

💡 Hint

Think about how code objects relate to database tables.

ORM stands for Object-Relational Mapping. It helps developers work with databases by mapping code objects to database tables, making database operations easier and more intuitive.

❓ component_behavior

intermediate

What will be the output of this Prisma query?

Given this Prisma client code, what will be the value of 'users' after execution?

Node.js

const users = await prisma.user.findMany({ where: { age: { gt: 18 } } });

A An array of user objects where each user is older than 18.

B A single user object with age exactly 18.

C An empty array because no users are returned without explicit select.

D A count of users older than 18.

💡 Hint

Look at the 'findMany' method and the 'where' filter.

The findMany method returns an array of all user records matching the condition. Here, it returns users with age greater than 18.

📝 Syntax

advanced

Which Sequelize model definition is syntactically correct?

Select the option that correctly defines a Sequelize model for a 'Product' with 'name' as string and 'price' as float.

A sequelize.define('Product', { name: DataTypes.STRING, price: DataTypes.FLOAT });

B sequelize.define('Product', { name: STRING, price: FLOAT });

C sequelize.define('Product', { name: Sequelize.STRING, price: Sequelize.FLOAT });

D sequelize.define('Product', { name: 'string', price: 'float' });

💡 Hint

Remember to use DataTypes for field types in Sequelize.

Sequelize requires using DataTypes to specify field types when defining models. Option A correctly uses DataTypes.STRING and DataTypes.FLOAT.

🔧 Debug

advanced

Why does this Prisma query throw an error?

Consider this Prisma query code snippet. Why does it throw a runtime error? const user = await prisma.user.findUnique({ where: { email: '[e-mail]' } }); console.log(user.name.toUpperCase());

A Because 'findUnique' requires an 'id' field, not 'email'.

B Because 'user' can be null if no record matches, so accessing 'name' causes an error.

C Because 'toUpperCase()' is not a valid method for strings in JavaScript.

D Because Prisma client does not support 'findUnique' method.

💡 Hint

Think about what happens if no user matches the email.

If no user matches the email, findUnique returns null. Trying to access name on null causes a runtime error.

❓ state_output

expert

What is the final state of the database after this Sequelize transaction?

Given this Sequelize transaction code, what will be the final state of the 'Orders' table if an error occurs during the second create call? const t = await sequelize.transaction(); try { await Order.create({ item: 'Book', quantity: 1 }, { transaction: t }); await Order.create({ item: null, quantity: 2 }, { transaction: t }); // item cannot be null await t.commit(); } catch (error) { await t.rollback(); } What happens to the 'Orders' table?

A Both orders are added, but the second has a null item field.

B Only the first order is added because it was created before the error.

C No new orders are added because the transaction is rolled back due to the error.

D The transaction commits partially, adding the first order and ignoring the error.

💡 Hint

Remember how transactions work when an error occurs.

Sequelize transactions ensure all operations succeed or none do. If an error occurs, the transaction rolls back, so no changes are saved.