[PHP知识库]PHP N+1问题

<?php
include '../mysql.php';

// N+1问题
// customer_rec表 customer_id 关联 customer表

$rec = $DB->query("select * from `customer_rec`");

$rec_id = array();
$cid = array();
$rec_data = array();

while ($recs = $DB->fetch_assoc($rec)){
    if (!in_array($recs['customer_id'],$rec_id)){
        $rec_id[] = $recs['customer_id'];
        $rec_data[$recs['customer_id']] = $recs;
    }
}

$c =  $DB->query("select * from `customer` where id in (".implode(',',$rec_id).")");
while ($rec = $DB->fetch_assoc($c)){
    $cid[$rec['id']] = $rec;
}

foreach ($rec_data as $data){
//    $rec_data[$data['customer_id']]['client_name'] = $cid[$data['customer_id']];  
    $rec_data[$data['customer_id']]['client_name'] = $cid[$data['customer_id']]['client_name'];
}

print_r($rec_data);