Eager loading (with) in Laravel - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the output of this Laravel eager loading code?

Given the following Eloquent query, what will be the number of queries executed when fetching posts with their comments eagerly loaded?

Post::with('comments')->get();

A 1 query executed: one for posts and their comments together

B 2 queries executed: one for posts and one for comments

C Multiple queries executed: one for each post's comments

D No queries executed until comments are accessed

💡 Hint

Eager loading loads related models in separate queries before accessing them.

Eager loading with 'with' runs one query for the main model (posts) and one query for the related model (comments). This avoids running a query for each post's comments (which would be lazy loading).

📝 Syntax

intermediate

Which option correctly eager loads nested relationships in Laravel?

You want to eager load the 'comments' relationship and, within comments, the 'author' relationship. Which code snippet is correct?

A Post::with('comments->author')->get();

B Post::with(['comments', 'author'])->get();

C Post::with('comments.author')->get();

D Post::with('comments')->with('author')->get();

💡 Hint

Use dot notation to eager load nested relationships.

The correct syntax to eager load nested relationships is to use dot notation inside the 'with' method as a string or array.

🔧 Debug

advanced

Why does this eager loading code cause an error?

Consider this code:

Post::with(['comments' => function($query) { $query->where('approved', true); }])->get();

What is the cause of the error if 'comments' is not a defined relationship on Post?

A The 'approved' column does not exist in the comments table, causing a database error.

B The closure syntax inside 'with' is invalid and causes a syntax error.

C The 'where' clause inside the closure is not allowed in eager loading.

D The 'comments' relationship is not defined on the Post model, causing a runtime error.

💡 Hint

Check if the relationship method exists on the model.

Eager loading requires the relationship method to be defined on the model. If 'comments' is missing, Laravel throws an error.

❓ state_output

advanced

What is the output count of comments when eager loading with a constraint?

Given this code:

$posts = Post::with(['comments' => fn($q) => $q->where('approved', true)])->get();
$count = $posts->first()->comments->count();

What does $count represent?

A The number of approved comments for the first post

B The total number of comments for all posts

C The total number of comments for the first post, ignoring approval

D Always zero because eager loading with constraints disables comments

💡 Hint

Eager loading constraints filter the related models loaded.

The closure inside 'with' filters comments to only those approved, so the comments collection contains only approved comments.

🧠 Conceptual

expert

Why prefer eager loading over lazy loading in Laravel?

Which is the main reason to use eager loading (with) instead of lazy loading when fetching related models in Laravel?

A To reduce the number of database queries and improve performance

B To load related models only when accessed to save memory

C To automatically cache related models for offline use

D To force Laravel to use raw SQL queries instead of Eloquent

💡 Hint

Think about how many queries run when accessing related data.

Eager loading reduces the number of queries by loading related data in fewer queries, avoiding the N+1 query problem.