How to Perform a `leftJoin` in an Eloquent Query

Table Of Contents

• When Eloquent Relationships Aren't Enough
• Laravel LeftJoin Patterns
• Advanced LeftJoin Techniques

When Eloquent Relationships Aren't Enough

Sometimes you need all users, even those without posts, along with their post counts. Regular Eloquent relationships only give you users who have posts. Enter leftJoin():

// Only users WITH posts (inner join behavior)
$usersWithPosts = User::whereHas('posts')->with('posts')->get();

// ALL users, with or without posts (left join)
$allUsersWithPostCounts = User::leftJoin('posts', 'users.id', '=', 'posts.user_id')
    ->select('users.*', DB::raw('COUNT(posts.id) as posts_count'))
    ->groupBy('users.id')
    ->get();

// More readable approach with join relationships
$usersWithOptionalPosts = User::leftJoin('posts', 'users.id', '=', 'posts.user_id')
    ->select([
        'users.id',
        'users.name', 
        'users.email',
        DB::raw('COALESCE(COUNT(posts.id), 0) as total_posts')
    ])
    ->groupBy('users.id', 'users.name', 'users.email')
    ->get();

Laravel LeftJoin Patterns

Different scenarios where leftJoin outperforms regular Eloquent relationships:

// E-commerce: Products with optional reviews
$productsWithReviews = Product::leftJoin('reviews', 'products.id', '=', 'reviews.product_id')
    ->select([
        'products.*',
        DB::raw('AVG(reviews.rating) as avg_rating'),
        DB::raw('COUNT(reviews.id) as review_count')
    ])
    ->groupBy('products.id')
    ->get();

// Blog: Categories with post counts (including empty categories)
$categoriesWithCounts = Category::leftJoin('posts', 'categories.id', '=', 'posts.category_id')
    ->select([
        'categories.id',
        'categories.name',
        'categories.slug',
        DB::raw('COUNT(posts.id) as posts_count')
    ])
    ->groupBy('categories.id', 'categories.name', 'categories.slug')
    ->orderBy('posts_count', 'desc')
    ->get();

// Multiple left joins for complex queries
$usersWithStats = User::leftJoin('posts', 'users.id', '=', 'posts.user_id')
    ->leftJoin('comments', 'users.id', '=', 'comments.user_id')
    ->leftJoin('likes', 'users.id', '=', 'likes.user_id')
    ->select([
        'users.*',
        DB::raw('COUNT(DISTINCT posts.id) as posts_count'),
        DB::raw('COUNT(DISTINCT comments.id) as comments_count'),
        DB::raw('COUNT(DISTINCT likes.id) as likes_count')
    ])
    ->groupBy('users.id')
    ->get();

// Conditional joins with where clauses
$activeUsersWithRecentPosts = User::leftJoin('posts', function ($join) {
        $join->on('users.id', '=', 'posts.user_id')
             ->where('posts.created_at', '>', now()->subDays(30));
    })
    ->select([
        'users.*',
        DB::raw('COUNT(posts.id) as recent_posts_count')
    ])
    ->where('users.active', true)
    ->groupBy('users.id')
    ->having(DB::raw('COUNT(posts.id)'), '>', 0)
    ->get();

Advanced LeftJoin Techniques

Handle complex data aggregation scenarios:

// Financial dashboard: Accounts with transaction summaries
$accountsWithBalances = Account::leftJoin('transactions', 'accounts.id', '=', 'transactions.account_id')
    ->select([
        'accounts.*',
        DB::raw('COALESCE(SUM(CASE WHEN transactions.type = "credit" THEN transactions.amount ELSE 0 END), 0) as total_credits'),
        DB::raw('COALESCE(SUM(CASE WHEN transactions.type = "debit" THEN transactions.amount ELSE 0 END), 0) as total_debits'),
        DB::raw('COALESCE(SUM(CASE WHEN transactions.type = "credit" THEN transactions.amount ELSE -transactions.amount END), 0) as balance')
    ])
    ->groupBy('accounts.id')
    ->get();

// Inventory management: Products with stock levels across warehouses
$productsWithInventory = Product::leftJoin('inventory', 'products.id', '=', 'inventory.product_id')
    ->leftJoin('warehouses', 'inventory.warehouse_id', '=', 'warehouses.id')
    ->select([
        'products.*',
        DB::raw('GROUP_CONCAT(CONCAT(warehouses.name, ":", COALESCE(inventory.quantity, 0)) SEPARATOR ", ") as warehouse_stock'),
        DB::raw('COALESCE(SUM(inventory.quantity), 0) as total_stock')
    ])
    ->groupBy('products.id')
    ->get();

// Performance comparison: leftJoin vs Eloquent relationships
// SLOWER - Multiple queries due to N+1
$usersEloquent = User::with('posts')->get()->map(function ($user) {
    return [
        'id' => $user->id,
        'name' => $user->name,
        'posts_count' => $user->posts->count()
    ];
});

// FASTER - Single query with leftJoin
$usersJoin = User::leftJoin('posts', 'users.id', '=', 'posts.user_id')
    ->select([
        'users.id',
        'users.name',
        DB::raw('COUNT(posts.id) as posts_count')
    ])
    ->groupBy('users.id', 'users.name')
    ->get();

// Debugging joins with toSql()
$query = User::leftJoin('posts', 'users.id', '=', 'posts.user_id')
    ->select('users.*', DB::raw('COUNT(posts.id) as posts_count'))
    ->groupBy('users.id');

dd($query->toSql()); // Shows the generated SQL

Use leftJoin() when you need all records from the main table regardless of relationship existence. Remember to use groupBy() with aggregate functions and COALESCE() to handle NULL values from unmatched left joins.

Related: Laravel Collections: Beyond Basic Array Operations | Advanced Eloquent Techniques and Optimizations in Laravel | Database Design Patterns: Complete Guide 2025 | Database Design: Fundamentals of Good Database Architecture | SQL Query Optimization: Indexing, Joins & Performance