Filtering arguments in GraphQL - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

Filtering users by age greater than 30

Given the following GraphQL query, what is the expected output if the database contains users with ages 25, 35, and 40?

GraphQL

query {
  users(age_gt: 30) {
    id
    name
    age
  }
}

A [{"id": "1", "name": "John", "age": 25}, {"id": "2", "name": "Alice", "age": 35}, {"id": "3", "name": "Bob", "age": 40}]

B [{"id": "1", "name": "John", "age": 25}]

C [{"id": "2", "name": "Alice", "age": 35}, {"id": "3", "name": "Bob", "age": 40}]

D []

💡 Hint

Think about which users have age greater than 30.

The filter age_gt: 30 returns only users whose age is greater than 30, so users aged 35 and 40 are included.

📝 Syntax

intermediate

Identify the syntax error in filtering by name

Which option contains a syntax error in this GraphQL query filtering users by name?

GraphQL

query {
  users(name_eq: "John") {
    id
    name
  }
}

A query { users(name_eq: John) { id name } }

B query { users(name_eq: "John") { id name } }

C } } eman di { )"nhoJ" :qe_eman(sresu { yreuq

D uery { users(name_eq: "John") { id name } }

💡 Hint

Check if string values are properly quoted.

In GraphQL, string arguments must be enclosed in double quotes. Option A misses quotes around John, causing a syntax error.

❓ optimization

advanced

Optimizing filtering with multiple arguments

Which query is the most efficient to filter users by age greater than 20 and name starting with 'A'?

A query { users(age_gt: 20, name_starts_with: "A") { id name age } }

B query { users { id name age } } # filter client-side

C query { users(age_gt: 20) { id name age } } # then filter name client-side

D query { users(name_starts_with: "A") { id name age } } # then filter age client-side

💡 Hint

Filtering on the server reduces data transfer and processing.

Applying both filters in the query reduces the amount of data sent and processed, making it more efficient.

🧠 Conceptual

advanced

Understanding filtering argument types

Which filtering argument type allows selecting records where a field value is within a list of values?

A contains (substring match)

B gt (greater than)

C eq (equals)

D in (within a list)

💡 Hint

Think about selecting multiple possible values for a field.

The 'in' argument filters records where the field matches any value in a given list.

🔧 Debug

expert

Debugging a filter that returns no results

A query filters users with age_lt: 18 but returns no results, even though the database has users aged 16 and 17. Which option explains the most likely cause?

GraphQL

query {
  users(age_lt: 18) {
    id
    name
    age
  }
}

A The database has no users younger than 18, so no results are returned.

B The filter argument 'age_lt' is not supported by the schema, so it is ignored.

C The query syntax is invalid, causing no results to be returned.

D The filter should be 'age_lt: "18"' with quotes around the number.

💡 Hint

Check if the filtering argument is defined in the schema.

If the schema does not support 'age_lt', the filter is ignored and no filtering happens, possibly returning no results.

Practice

1.

What is the main purpose of filtering arguments in a GraphQL query?

easy

A. To get only the data you need by specifying conditions

B. To change the structure of the data returned

C. To add new data to the database

D. To delete data from the database

Solution

1. Step 1: Understand filtering arguments

   Filtering arguments are used to specify conditions that limit the data returned by a query.

2. Step 2: Identify the purpose in the context of data retrieval

   They help get only the data you need, making queries efficient and faster.

3. Final Answer:

   To get only the data you need by specifying conditions -> Option A

4. Quick Check:

   Filtering arguments = get needed data [OK]

Hint: Filtering arguments limit data returned by conditions [OK]

Common Mistakes:

• Thinking filtering changes data structure
• Confusing filtering with data modification
• Assuming filtering adds or deletes data

2.

Which of the following is the correct syntax to filter users by age greater than 25 in a GraphQL query?

{
  users(age_gt: 25) {
    id
    name
  }
}

easy

A. { users(age: {gt: 25}) { id name } }

B. { users(age_gt: 25) { id name } }

C. { users(filter: {age: 25}) { id name } }

D. { users(age > 25) { id name } }

Solution

1. Step 1: Identify correct GraphQL filter syntax

   GraphQL uses argument names like age_gt to filter values greater than 25.

2. Step 2: Compare options with standard syntax

   { users(age_gt: 25) { id name } } uses age_gt: 25 correctly; others use invalid or incorrect syntax.

3. Final Answer:

   { users(age_gt: 25) { id name } } -> Option B

4. Quick Check:

   Correct filter syntax = { users(age_gt: 25) { id name } } [OK]

Hint: Use _gt suffix for 'greater than' filters [OK]

Common Mistakes:

• Using operators like > inside arguments
• Passing filter as nested object incorrectly
• Using equality instead of greater than

3.

Given the query below, what will be the output if the database has users with ages 20, 30, and 40?

{
  users(age_gte: 30) {
    name
  }
}

medium

A. [{"name": "User30"}, {"name": "User40"}]

B. [{"name": "User20"}]

C. [{"name": "User20"}, {"name": "User30"}, {"name": "User40"}]

D. []

Solution

1. Step 1: Understand the filter age_gte: 30

   This filter returns users with age greater than or equal to 30.

2. Step 2: Check which users match the condition

   Users with ages 30 and 40 match; user with age 20 does not.

3. Final Answer:

   [{"name": "User30"}, {"name": "User40"}] -> Option A

4. Quick Check:

   age_gte 30 returns users 30 and 40 [OK]

Hint: gte means greater than or equal [OK]

Common Mistakes:

• Including users younger than 30
• Confusing gte with gt
• Returning empty list incorrectly

4.

Identify the error in the following GraphQL query that tries to filter products by price less than 100:

{
  products(price_lt 100) {
    id
    name
  }
}

medium

A. Incorrect field name 'products' instead of 'productList'

B. Using wrong filter suffix 'lt' instead of 'lessThan'

C. Missing curly braces around filter argument

D. Missing colon ':' between argument name and value

Solution

1. Step 1: Check argument syntax in the query

   The argument price_lt 100 is missing a colon ':' between the argument name and value.

2. Step 2: Confirm correct syntax for filtering

   Correct syntax requires a colon: price_lt: 100.

3. Final Answer:

   Missing colon ':' between argument name and value -> Option D

4. Quick Check:

   Arguments need ':' separator [OK]

Hint: Always use ':' between argument and value [OK]

Common Mistakes:

• Omitting colon ':' after argument name
• Using wrong filter suffix names
• Confusing field names

5.

You want to query a list of books published after 2010 and with more than 300 pages. Which of the following GraphQL queries correctly applies both filters?

{
  books(published_gt: 2010, pages_gt: 300) {
    title
    author
  }
}

hard

A. { books(filter: {published: {gt: 2010}, pages: {gt: 300}}) { title author } }

B. { books(published: {gt: 2010}, pages: {gt: 300}) { title author } }

C. { books(published_gt: 2010, pages_gt: 300) { title author } }

D. { books(published_gt: 2010 pages_gt: 300) { title author } }

Solution

1. Step 1: Understand how to apply multiple filters in GraphQL

   Filters are passed as separate arguments separated by commas.

2. Step 2: Check each option for correct syntax and filter usage

   { books(published_gt: 2010, pages_gt: 300) { title author } } correctly uses commas and proper filter names; others have syntax errors or wrong structure.

3. Final Answer:

   { books(published_gt: 2010, pages_gt: 300) { title author } } -> Option C

4. Quick Check:

   Multiple filters use commas and correct suffixes [OK]

Hint: Separate filters with commas and use _gt suffix [OK]

Common Mistakes:

• Missing commas between arguments
• Using nested filter objects incorrectly
• Omitting colons between argument and value