php优化查询foreach代码实例讲解

// $datas 要返回的数据
foreach ($datas as $_v) {
  // todo 在foreach中查询了两次 **time**: 290 ms(postman)
  $uid = $_v->uid;
  $_v->user_name  = User::find($uid)->username; // 1
  $_v->user_avatar = User::find($uid)->avatar;  // 2
}

foreach ($datas as $_v) {
  // todo
  // 简单的优化使得两次sql查询变成一次
  // 在foreach中查询了一次 **time**: 230 ms(postman)
  $user = User::find($_v->uid));   // 1
  $_v->user_name  = $user->username;
  $_v->user_avatar = $user->avatar;
}

// $tmp_data_arr 是存储在foreach外面执行的数据库查询结果
foreach ($tmp_data_arr as $value) {
  foreach ($datas as $_v) {
    if ($_v->uid === $value['id']) { // **time**: 180 ms(postman)
      $_v->user_name  = $value['username'];
      $_v->user_avatar = $value['avatar'];
    }
  }
}

// 返回数据
return $datas;