Hello, coders! Today, we’ll dive into an engaging subject, one that has baffled Laravel developers quite a few times. We’ll explore how to get the SUM of a relation column using Laravel’s Eloquent ORM, without the need to load the entire data from a related model.
This issue has left many scratching their heads, and I can bet a number of us have seen this problem before. So, let’s grab our detective glasses and unravel this mystery together, the Laravel way.
Our Conundrum: Getting the SUM without Loading the Whole Data
Imagine you have two models in your Laravel project: Account and Transaction. An Account can have many transactions. You want to get the accounts and eager load only the sum of the amounts on the related Transaction table.
<table> <tr> <th>accounts</th> <th>transactions</th> </tr> <tr> <td>id, name, address</td> <td>id, account_id, amount</td> </tr> </table>
In this scenario, you’d usually use Laravel’s Eloquent relationships, specifically the hasMany()
method, to define this relationship in your Account model like so:
public function transactions() { return $this->hasMany(‘App\Models\Transaction’, ‘account_id’); }
You can then call on your transactions related to a particular account using the with(['transactions'] )
method. To get the sum of ‘amount’ from the transactions, you can use a simple foreach loop:
$accounts = Account::with([‘transactions’] )->get(); foreach ($accounts as $key => $value) { echo $value->transactions->sum(‘amount’). ” <br />”; }
This works, but the issue here is, you’re loading all transactions just to get the sum of the ‘amount’ field. If your transactions data is massive, this could pose performance issues. You need a more efficient solution.
Solution 1: Use Subqueries
A neat way around this is to use subqueries. Subqueries allow you to perform calculations on your related models without loading all the related data. It’s a more efficient way to get your result.
Here’s how to do it:
$amountSum = Transaction::selectRaw(‘sum(amount)’)
->whereColumn(‘account_id’, ‘accounts.id’)
->getQuery();
$accounts = Account::select(‘accounts.*’)
->selectSub($amountSum, ‘amount_sum’)
->get();
foreach($accounts as $account) {
echo $account->amount_sum;
}
Solution 2: Leverage Eloquent’s Builder Macro
Alternatively, you can extend Eloquent’s query builder via a macro. Macros give you the ability to add on custom functions to Laravel’s internal classes. In this case, you can create a withSum
macro to get the sum of a related model’s column:
// Code to implement the ‘withSum’ macro goes here
$accounts = Account::withSum(‘transactions.amount’)->get();
foreach($accounts as $account) {
echo $account->transactions_amount_sum;
}
Solution 3: Use Eloquent’s withCount
Method
Although it’s typically used for counting related records, Laravel’s withCount
method can be customized to sum a column instead:
$accounts = Account::withCount([ ‘transactions as transactions_amount_sum’ => function ($query) { $query->select(DB::raw(“SUM(amount)”)); } ] )->get(); foreach($accounts as $account) { echo $account->transactions_amount_sum; }
In the withCount
method, we define a customized count query as an array element. This query will run a SUM operation instead of a COUNT, and the result is aliased as transactions_amount_sum
.
Solution 4: Creating a Custom Accessor in the Model
If you frequently need the sum of transactions for an account, consider adding a custom accessor to your Account model. This accessor will automatically calculate the sum whenever you access the related attribute.
class Account extends Model
{
public function getTransactionsSumAttribute()
{
return $this->transactions()->sum(‘amount’);
}
}
Now, you can directly access the sum of transactions for any account:
$account = Account::find(1);
echo $account->transactions_sum;
This approach results in an extra query for each account when calculating the sum, which might not be efficient for a large number of accounts. Therefore, consider using this method when dealing with a limited number of records.
Solution 5: Using Raw SQL Expressions
Although Eloquent provides a convenient and readable way to create queries, sometimes you might need to resort to raw SQL for more complex cases:
$accounts = DB::table(‘accounts’)
->leftJoin(‘transactions’, ‘accounts.id’, ‘=’, ‘transactions.account_id’)
->select(‘accounts.*’, DB::raw(‘SUM(transactions.amount) as transactions_amount_sum’))
->groupBy(‘accounts.id’)
->get();
foreach($accounts as $account) {
echo $account->transactions_amount_sum;
}
Remember, raw SQL queries skip some of the security checks performed by Eloquent and may be more prone to SQL injection attacks. Always make sure your raw SQL queries are safe and secure.
Whichever solution you choose, remember the goal: Write clean, efficient, and readable code that not only solves your problem but also can be understood by others (and by you, six months down the line!).
Conclusion
Laravel’s powerful Eloquent ORM, tackling complex database operations is simplified and easily manageable. The process of finding the sum of related model data does not need to be a daunting task. Depending on the specific requirements and efficiency considerations, different methods can be applied.
In the scenarios we’ve discussed, we started with using a subquery to get the sum of transactions. Then, we explored using a custom withSum
macro to extend Eloquent, and then proceeded to show how withCount
method could be repurposed for our goal. After that, we dived into creating a custom accessor to perform the sum directly on the model and finally, we looked into raw SQL queries when we need absolute control over our database operations.
Choosing the right solution will depend heavily on your specific situation. Some solutions are more efficient in terms of database queries but come with the cost of being harder to read or understand. Others are straightforward but may not be the most efficient in large-scale applications. As a developer, it’s crucial to understand these trade-offs and make an informed decision that best fits your needs.
Understanding Laravel and its Eloquent ORM is an ongoing journey. As you gain experience and face more challenging problems, you’ll discover and invent new ways to leverage its power. Laravel’s versatility and adaptability are what makes it one of the most popular PHP frameworks out there.