Why databases back GraphQL - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a GraphQL query that fetches all users.

GraphQL

type Query { users: [1] }

Drag options to blanks, or click blank then click option'

A[User]

BUser

CString

DInt

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'User' instead of '[User]' which returns a single user, not a list.

Using scalar types like String or Int for a list of users.

The users query returns a list of User objects, so the type is [User].

2fill in blank

medium

Complete the resolver function to fetch users from the database.

GraphQL

const resolvers = { Query: { users: async () => await [1].find() } }

Drag options to blanks, or click blank then click option'

AGraphQL

BUserModel

Cdatabase

DfetchUsers

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'database' or 'GraphQL' which are not the model names.

Using a function name like 'fetchUsers' instead of the model.

The resolver calls the database model UserModel to find all users.

3fill in blank

hard

Fix the error in the GraphQL schema to correctly define a user type with id and name.

GraphQL

type User { id: ID! name: [1]! }

Drag options to blanks, or click blank then click option'

AInt

BFloat

CBoolean

DString

Attempts:

3 left

💡 Hint

Common Mistakes

Using Int or Boolean for name which are incorrect types.

Using Float which is for decimal numbers.

The name field should be a String type in GraphQL.

4fill in blank

hard

Fill both blanks to write a resolver that fetches a user by id from the database.

GraphQL

const resolvers = { Query: { user: async (_, [1]) => await UserModel.[2]({ id: id }) } }

Drag options to blanks, or click blank then click option'

Aargs

Bparams

CfindOne

DfindAll

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'params' instead of 'args' for resolver arguments.

Using 'findAll' which returns multiple records instead of one.

The resolver receives arguments as 'args' and uses 'findOne' to get a single user by id.

5fill in blank

hard

Fill all three blanks to define a mutation that adds a new user with name and returns the created user.

GraphQL

type Mutation { addUser(name: [1]!): [2] } const resolvers = { Mutation: { addUser: async (_, [3]) => { const user = new UserModel({ name: name }); await user.save(); return user; } } }

Drag options to blanks, or click blank then click option'

AString

BUser

Cargs

DInt

Attempts:

3 left

💡 Hint

Common Mistakes

Using Int for name which should be String.

Returning a scalar instead of User type.

Using wrong parameter name instead of 'args'.

The mutation takes a name of type String, returns a User type, and receives arguments as 'args'.

Practice

1. Why do GraphQL APIs usually connect to databases?

easy

A. To speed up the internet connection

B. To make the app's user interface colorful

C. To store and organize the data that apps request

D. To create animations in the app

Solution

1. Step 1: Understand GraphQL's role

   GraphQL lets apps ask for specific data they need.

2. Step 2: Identify why databases are needed

   Databases store and organize data safely for GraphQL to fetch.

3. Final Answer:

   To store and organize the data that apps request -> Option C

4. Quick Check:

   GraphQL needs data storage = To store and organize the data that apps request [OK]

Hint: GraphQL fetches data; databases keep data safe [OK]

Common Mistakes:

• Thinking GraphQL creates UI effects
• Confusing data storage with internet speed
• Assuming GraphQL handles animations

2. Which of the following is the correct way to describe how GraphQL queries data from a database?

easy

A. GraphQL sends a query to the database asking for specific fields

B. GraphQL directly edits the database tables without queries

C. GraphQL stores data inside the app without using a database

D. GraphQL only works with files, not databases

Solution

1. Step 1: Understand GraphQL query behavior

   GraphQL sends queries specifying exactly which data fields it wants.

2. Step 2: Check database interaction

   Databases respond to these queries by returning requested data.

3. Final Answer:

   GraphQL sends a query to the database asking for specific fields -> Option A

4. Quick Check:

   GraphQL queries database fields = GraphQL sends a query to the database asking for specific fields [OK]

Hint: GraphQL queries, doesn't edit database directly [OK]

Common Mistakes:

• Thinking GraphQL edits database tables directly
• Believing GraphQL stores data locally only
• Assuming GraphQL works without databases

3. Given this GraphQL query:
{ user(id: 1) { name, email } }
What does the database return?

medium

A. User with id 1's name and email only

B. All users with their names and emails

C. An error because the query is incomplete

D. User with id 1's password and email

Solution

1. Step 1: Analyze the query fields

   The query asks for user with id 1, requesting only name and email fields.

2. Step 2: Understand database response

   The database returns data matching id 1 with only requested fields: name and email.

3. Final Answer:

   User with id 1's name and email only -> Option A

4. Quick Check:

   Query requests specific user fields = User with id 1's name and email only [OK]

Hint: Query fields limit data returned from database [OK]

Common Mistakes:

• Assuming all users are returned
• Expecting password field without request
• Thinking query is incomplete and errors

4. A developer wrote this GraphQL query:
{ product(id: ) { name price } }
What is the main issue?

medium

A. GraphQL does not support querying products

B. Query will return all products instead of one

C. Fields name and price are invalid

D. Missing value for id causes syntax error

Solution

1. Step 1: Check query syntax

   The id argument is empty, which is invalid syntax in GraphQL.

2. Step 2: Understand error impact

   This causes a syntax error, so the query won't run or return data.

3. Final Answer:

   Missing value for id causes syntax error -> Option D

4. Quick Check:

   Empty argument value = syntax error [OK]

Hint: Always provide values for required arguments [OK]

Common Mistakes:

• Assuming query returns all products
• Thinking fields are invalid
• Believing GraphQL can't query products

5. An app uses GraphQL to fetch user data from a database. The query requests { user(id: 5) { name, posts { title } } }. Why is the database important here?

hard

A. It creates the GraphQL query automatically

B. It stores user and post data so GraphQL can fetch nested info

C. It styles the user interface with data colors

D. It speeds up the app by skipping data storage

Solution

1. Step 1: Understand nested query

   The query asks for user info and their posts' titles, which is nested data.

2. Step 2: Role of database

   The database holds both user and post data, allowing GraphQL to retrieve nested related data.

3. Final Answer:

   It stores user and post data so GraphQL can fetch nested info -> Option B

4. Quick Check:

   Database stores nested data = It stores user and post data so GraphQL can fetch nested info [OK]

Hint: Database holds nested data GraphQL queries [OK]

Common Mistakes:

• Thinking database creates queries
• Confusing data storage with UI styling
• Assuming database skips storing data