Fetch Specific Related Attributes with withAggregate()

Use withAggregate() to pull a single column value from a relationship via a SQL subquery without eager loading full model instances.

When you need a single attribute from a related model, eager loading the entire relationship into memory wastes memory and hydration overhead.

Laravel's withAggregate() runs a correlated subquery directly in the primary SQL statement, attaching the result as a virtual attribute on each parent model.

Code Examples

use App\Models\Post;

// 1. Pull a single related column (creates $post->user_name)
$posts = Post::withAggregate('user', 'name')->get();

// 2. Custom alias using the 'relation as alias' syntax
$posts = Post::withAggregate('user as author_email', 'email')->get();
// Accessible as: $post->author_email

// 3. Aggregate functions (MAX, MIN, AVG, SUM) with custom alias
$posts = Post::withAggregate('comments as latest_comment_at', 'created_at', 'max')->get();
// Accessible as: $post->latest_comment_at

Key Benefits

• Method Signature: Accepts ($relations, $column, $function = null). Aliases must be specified in the relation argument using 'relation as alias'.
• Zero Hydration Overhead: Attaches single column values without instantiating full Eloquent model objects for related rows.
• Underlying Engine: Serves as the flexible foundation behind withCount(), withMax(), and withAvg().
• Direct SQL Sorting: You can order by the virtual attribute directly in SQL: ->orderBy('latest_comment_at', 'desc').