我正在使用LARAVEL 5.6
我正在使用口才。我想一起使用GROUP BY和ORDER BY，我有一些经验告诉我，即使在mysql查询中，它也不像看起来那样简单；）。
我也读过类似的问题，但是我仍然很困惑！
我有两个名为Currency（数据库表：currencies）和CurrencyExchangeRate（数据库表：currency_exchange_rates）的模型（表），其信息如下：
Schema::create('currencies', function (Blueprint $table) {
$table->increments('id');
$table->string('title', 200)->nullable();
$table->string('symbol', 20)->nullable();
$table->text('icon')->nullable();
$table->tinyInteger('visible')->defualt(0);
$table->tinyInteger('order')->nullable();
$table->bigInteger('created_at');
$table->bigInteger('updated_at');
});
和
Schema::create('currency_exchange_rates', function (Blueprint $table) {
$table->increments('id');
$table->integer('currency_id')->unsigned();
$table->foreign('currency_id')->references('id')->on('currencies')->onDelete('cascade');
$table->bigInteger("sell")->nullable();
$table->bigInteger("buy")->nullable();
$table->string('date', 20);
$table->bigInteger('created_at');
$table->bigInteger('updated_at');
});
这些是我的模特：
class Currency extends Model
{
/**
* The storage format of the model's date columns.
*
* @var string
*/
public $dateFormat = 'U';
protected $fillable = ['title', 'symbol', 'icon', 'visible', 'order'];
public function exchangeRate()
{
return $this->hasMany('App\CurrencyExchangeRate');
}
public function getIconAttribute($value)
{
return json_decode($value);
}
}
和
class Currency extends Model
{
/**
* The storage format of the model's date columns.
*
* @var string
*/
public $dateFormat = 'U';
protected $fillable = ['title', 'symbol', 'icon', 'visible', 'order'];
public function exchangeRate()
{
return $this->hasMany('App\CurrencyExchangeRate');
}
public function getIconAttribute($value)
{
return json_decode($value);
}
}
如您所见，每种货币可以有多种货币汇率，我想显示用户在过去10天中的货币汇率！ 一天中某货币的汇率不同，我希望一天中输入的最后一个汇率！例如：
id | currency_id | sell | buy | date | created_at | updated_at
---+-------------+------+-----+------------+-------------+------------
1 | 1 | 10 | 12 | 2018-04-05 | 1 | 1
2 | 1 | 11 | 13 | 2018-04-05 | 2 | 2
3 | 1 | 15 | 20 | 2018-04-05 | 3 | 3
您看到currency_id = 1中的date = 2018-04-05有4个费率，在我的报告中，我需要最新的费率（created_at = 3 | Sell = 15 | buy = 20）
因此，如果我想有一个更真实的示例，我的表将如下所示：
id | currency_id | sell | buy | date | created_at | updated_at
---+-------------+------+-----+------------+-------------+------------
1 | 1 | 10 | 12 | 2018-04-05 | 1 | 1
2 | 1 | 11 | 13 | 2018-04-05 | 2 | 2
3 | 1 | 15 | 20 | 2018-04-05 | 3 | 3
4 | 1 | 20 | 22 | 2018-04-06 | 4 | 4
5 | 1 | 21 | 23 | 2018-04-06 | 5 | 5
6 | 2 | 40 | 50 | 2018-04-05 | 1 | 1
7 | 2 | 60 | 70 | 2018-04-05 | 2 | 2
8 | 2 | 80 | 90 | 2018-04-06 | 4 | 4
9 | 2 | 95 | 85 | 2018-04-06 | 5 | 5
我想要一个像这样的数组：
$currencies = [
'currency_id ' => 1,
'title' => 'Dollar',
'currency_exchange_rates' => [
'2018-04-05' => [
'sell' => 15,
'buy' => 20,
'created_at' => 3, // the latest rate entered in 2018-04-06 for 'currency_id ' => 1
] ,
'2018-04-06' => [
'sell' => 21,
'buy' => 23,
'created_at' => 5, // the latest rate entered in 2018-04-06 for 'currency_id ' => 1
]
] ,
'currency_id ' => 2,
'title' => 'Euro',
'currency_exchange_rates' => [
'2018-04-05' => [
'sell' => 60,
'buy' => 70,
'created_at' => 2, // the latest rate entered in 2018-04-05 for 'currency_id ' => 2
] ,
'2018-04-06' => [
'sell' => 95 ,
'buy' => 85,
'created_at' => 5, // the latest rate entered in 2018-04-06 for 'currency_id ' => 2
]
]
];
我已使用此代码通过id获取每种货币的货币汇率：
$days = 10 ;
$currencies = Currency::findOrFail($currency_id)
->with(
[
'exchangeRate' => function ($q) use ($days) {
$q->orderBy('created_at', 'DESC')
->where('created_at', ">", strtotime('-' . $days . ' days', time()))
->groupBy('date')
->get();
}
]
)->get();
但是ORDER BY无法正常工作，我只会得到一流的价格。
更新
我想获取最近10天中每个天的最新汇率，例如，如果管理员在USD上为2018-04-05输入了4个汇率，我想要获得最新的！ （为简化示例，我只输入了sell汇率）
USD = [
2018-04-01 => 10 (the latest rate has been entered for USD on 2018-04-01 is 10),
2018-04-02 => 13 (the latest rate has been entered for USD on 2018-04-02 is 13),
2018-04-03 => 15 (the latest rate has been entered for USD on 2018-04-03 is 15),
2018-04-04 => 18 (the latest rate has been entered for USD on 2018-04-04 is 18),
2018-04-05 => 12 (the latest rate has been entered for USD on 2018-04-05 is 12),
...
],
EUR = [
2018-04-01 => 10 (the latest rate has been entered for EUR on 2018-04-01 is 10),
2018-04-02 => 13 (the latest rate has been entered for EUR on 2018-04-02 is 13),
2018-04-03 => 15 (the latest rate has been entered for EUR on 2018-04-03 is 15),
2018-04-04 => 18 (the latest rate has been entered for EUR on 2018-04-04 is 18),
2018-04-05 => 12 (the latest rate has been entered for EUR on 2018-04-05 is 12),
...
],
答案 0 :(得分：1)
使用子查询联接：
$days = 10 ;
$currencies = Currency::with(
[
'exchangeRate' => function ($q) use ($days) {
$latest = CurrencyExchangeRate::select('currency_id', 'date')
->selectRaw('MAX(created_at) created_at')
->groupBy('currency_id', 'date');
$q->joinSub($latest, 'latest', function($join) {
$join->on('currency_exchange_rates.currency_id', 'latest.currency_id')
->on('currency_exchange_rates.date', 'latest.date')
->on('currency_exchange_rates.created_at', 'latest.created_at');
})->where('currency_exchange_rates.created_at', ">", strtotime('-' . $days . ' days', time()));
}
]
)->get();
这将执行以下查询：
select *
from `currency_exchange_rates`
inner join (
select `currency_id`, `date`, MAX(created_at) created_at
from `currency_exchange_rates`
group by `currency_id`, `date`
) as `latest`
on `currency_exchange_rates`.`currency_id` = `latest`.`currency_id`
and `currency_exchange_rates`.`date` = `latest`.`date`
and `currency_exchange_rates`.`created_at` = `latest`.`created_at`
where `currency_exchange_rates`.`currency_id` in (?, ...)
and `currency_exchange_rates`.`created_at` > ?
答案 1 :(得分：-1)
尝试
Currency::findOrFail($currency_id)
->with(
[
'exchangeRate' => function ($q) use ($days) {
$q->orderBy('created_at', 'DESC')
->first();
}
]
)->get();
这是我想的唯一方法