Query optimization in Laravel - Mini Project: Build & Apply

Query Optimization in Laravel

📖 Scenario: You are building a Laravel application that shows a list of books with their authors. You want to make sure the database queries are efficient to keep the app fast.

🎯 Goal: Learn how to optimize Laravel database queries by using eager loading to reduce the number of queries.

📋 What You'll Learn

Create a Book model with a relationship to Author

Set a variable for the maximum number of books to fetch

Write a query to get books with their authors using eager loading

Return the books data ready for display

💡 Why This Matters

🌍 Real World

Optimizing database queries in Laravel apps improves speed and user experience, especially when dealing with related data.

💼 Career

Understanding eager loading and query limits is essential for Laravel developers to write efficient, scalable applications.

1

Create the Book model with author relationship

Create a Laravel Book model class with a method author() that defines a belongsTo relationship to the Author model.

Laravel

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Model;

class Book extends Model
{
    // Define author relationship here
}

Hint

Use belongsTo inside the author() method to link to the Author model.

2

Set the maximum number of books to fetch

Create a variable called $maxBooks and set it to 10 to limit the number of books fetched.

Laravel

belongsTo(Author::class);
    }
}

// Set the maximum number of books to fetch
// Your code here

Hint

Just create a variable $maxBooks and assign it the number 10.

3

Write a query to get books with authors using eager loading

Write a Laravel query using the Book model to get books with their authors using with('author') and limit the results to $maxBooks. Store the result in a variable called $books.

Laravel

belongsTo(Author::class);
    }
}

$maxBooks = 10;

// Get books with authors using eager loading
// Your code here

Hint

Use Book::with('author')->limit($maxBooks)->get() to fetch books and their authors efficiently.

4

Return the books data for display

Return the $books variable from a controller method or function to complete the data retrieval process.

Laravel

belongsTo(Author::class);
    }
}

$maxBooks = 10;

$books = Book::with('author')->limit($maxBooks)->get();

// Return the books data
// Your code here

Hint

Simply write return $books; to complete the data retrieval.

Practice

1. What is the main benefit of using eager loading in Laravel queries?

easy

A. It reduces the number of database queries by loading related data upfront.

B. It automatically caches all query results for faster access.

C. It encrypts the query results for security.

D. It sorts the query results alphabetically.

Solution

1. Step 1: Understand eager loading purpose

   Eager loading loads related data in one query instead of many separate queries.

2. Step 2: Identify benefit in query optimization

   By reducing the number of queries, it speeds up the app and lowers database load.

3. Final Answer:

   It reduces the number of database queries by loading related data upfront. -> Option A

4. Quick Check:

   Eager loading = fewer queries [OK]

Hint: Eager loading means load related data once, not many times [OK]

Common Mistakes:

• Confusing eager loading with caching
• Thinking it sorts or encrypts data
• Believing it loads data lazily

2. Which of the following is the correct way to select only the 'name' and 'email' columns from the users table in Laravel?

easy

A. $users = DB::table('users')->select('name', 'email')->get();

B. $users = DB::table('users')->columns('name', 'email')->fetch();

C. $users = DB::table('users')->only('name', 'email')->all();

D. $users = DB::table('users')->pick('name', 'email')->fetchAll();

Solution

1. Step 1: Recall Laravel query builder syntax

   The method to specify columns is select(), and to get results is get().

2. Step 2: Match correct syntax

   $users = DB::table('users')->select('name', 'email')->get(); uses select('name', 'email')->get(), which is correct Laravel syntax.

3. Final Answer:

   $users = DB::table('users')->select('name', 'email')->get(); -> Option A

4. Quick Check:

   Select columns = select() + get() [OK]

Hint: Use select() to pick columns, then get() to fetch [OK]

Common Mistakes:

• Using non-existent methods like columns() or only()
• Confusing fetch() with get()
• Trying to fetch all columns without select()

3. Given the code below, what will be the number of queries executed?

Post::with('comments')->where('status', 'published')->get();

medium

A. 1 query

B. Number of comments queries

C. Number of posts + 1 queries

D. 2 queries

Solution

1. Step 1: Understand eager loading with 'with'

   The with('comments') loads related comments in a separate query.

2. Step 2: Count queries executed

   One query fetches posts with status 'published', second query fetches all related comments.

3. Final Answer:

   2 queries -> Option D

4. Quick Check:

   with() = 2 queries [OK]

Hint: with() runs 2 queries: main + related data [OK]

Common Mistakes:

• Thinking with() runs only 1 query
• Assuming one query per post for comments
• Confusing with() with lazy loading

4. Identify the problem in this Laravel query that causes slow performance:

$users = User::all();
foreach ($users as $user) {
  echo $user->profile->bio;
}

medium

A. The profile relation does not exist in User model.

B. The foreach loop syntax is incorrect.

C. Using all() loads all users without eager loading profiles, causing N+1 queries.

D. Using echo inside loop slows down PHP execution.

Solution

1. Step 1: Analyze query and loop

   User::all() loads all users but does not load related profiles eagerly.

2. Step 2: Identify N+1 query problem

   Accessing $user->profile inside loop triggers one query per user, causing many queries.

3. Final Answer:

   Using all() loads all users without eager loading profiles, causing N+1 queries. -> Option C

4. Quick Check:

   all() without eager loading = N+1 queries [OK]

Hint: Use with('profile') to avoid N+1 queries [OK]

Common Mistakes:

• Blaming loop syntax instead of query
• Assuming profile relation missing without checking
• Thinking echo slows query performance

5. You want to optimize a query that fetches posts with their authors and comments, but only need the post title, author name, and comment content. Which approach is best?

hard

A. Run separate queries for posts, authors, and comments and merge results in PHP.

B. Use eager loading with select() on posts, authors, and comments to fetch only needed columns.

C. Use lazy loading to fetch authors and comments only when accessed.

D. Fetch all posts, authors, and comments without filtering columns to avoid missing data.

Solution

1. Step 1: Understand data needed

   Only post title, author name, and comment content are required, so select only these columns.

2. Step 2: Apply eager loading with column selection

   Use with() to eager load authors and comments, and select() to limit columns for optimization.

3. Final Answer:

   Use eager loading with select() on posts, authors, and comments to fetch only needed columns. -> Option B

4. Quick Check:

   Eager load + select columns = best optimization [OK]

Hint: Combine eager loading and select() to fetch only needed data [OK]

Common Mistakes:

• Fetching all columns wastes resources
• Using lazy loading causes many queries
• Merging in PHP is slower than optimized queries