Codeigniter 4 Model Relationship Entity - codeigniter-4

Question

I have database tables that look like this : Table 1 : transaction
id|buyer_id|transaction_date
----------------------------
1 | 1 |2020-01-01
2 | 4 |2020-03-04
3 | 6 |2020-11-12
----------------------------
Table 2 : transaction_detail
id|transaction_id|item_id|qty
--------------------------------
1| 1 | 1 | 3 |
2| 1 | 4 | 1 |
3| 1 | 6 | 2 |
--------------------------------
transaction_detai.transaction_id is a foreign key to transaction.id
How can I select data in transaction table but also get all the transaction_detail as a child ? If I use join, it will generate all data in one row. I need something just like this :
Array(
[0] => Master\Entities\Transaction Object
(
[id:protected] =>
[buyer_id:protected] =>
[transaction_date:protected] =>
[transaction_detail:protected]=>
Array(
[0] => Master\Entities\TransactionDetail Object
(
[id:protected] =>
[transaction_id:protected] =>
[item_id:protected] =>
[qty:protected] =>
)
)
)
)

Answer 1

Your Context not clear whether you need it be done with model or with query builders. Using builders you can create a multidimensional array and place details accordingly and sample code for that is as:
$db = \Config\Database::connect();
// Fetch all details from main table say `transaction`
$dataMain = $db->table('transaction')
->where('transaction.deleted_at',NULL)
->select('transaction.id,
transaction.buyer_id,transaction.transaction_date')
->get()
->getResult();
$result = [];
foreach($dataMain as $dataRow){
// For each master table row generate two sub array one to store main table row and other to hold details table data respective to main table row
if(!isset($result[$dataRow->id])){
$result[$dataRow->id]['transaction'] = [];
$result[$dataRow->id]['transaction_details'] = [];
array_push($result[$dataRow->id]['transaction'],$dataRow);
}
$dataSecondary = $db->table('transaction_detail')
->where('transaction_detail.deleted_at',NULL)
->select('transaction_detail.id,
transaction_detail.transaction_id,
transaction_detail.item_id,transaction_detail.qty')
->where('transaction_detail.offer_id',$dataRow->id)
->get()
->getResult();
array_push($result[$dataRow->id]['transaction_details'],$dataSecondary);
}
// $result[$id]['transaction'] - contains master table data
// $result[$id]['transaction_details'] - contains sub table datas associated with respective master table data
print '<pre>';
var_dump($result);
exit;