Laravel 查询构建器 - 从另一个表中选择前 1 行

Question

我有这个用于 MySQL 的 SQL 查询，它运行良好。但是我需要使用查询生成器重写它，并且需要完全避免DB::raw()，因为开发数据库与生产数据库不同。我知道远非理想，但不幸的是它就是这样。

SELECT athletes.*, 
     (
         SELECT performance
         FROM performances
         WHERE athletes.id = performances.athlete_id AND performances.event_id = 1
         ORDER BY performance DESC
         LIMIT 0,1
     ) AS personal_best
FROM athletes
ORDER BY personal_best DESC
Limit 0, 100

我正在努力如何重写personal_best 部分。我有运动员的成绩表，我只需要选择每个运动员的最佳成绩作为他的个人最好成绩。

我试图搜索答案，但我找到的所有答案都包括原始添加原始 SQL。

任何想法或提示将不胜感激。

提前谢谢你！

所以我接受了我可能不得不为此使用 Eloquent，但仍然无法取得进展。这是我的代码：

class Athlete extends Model
{
    /**
     * The table associated with the model.
     *
     * @var string
     */
    protected $table = 'athletes';

    /**
     * The primary key associated with the table.
     *
     * @var string
     */
    protected $primaryKey = 'id';

    /**
     * Indicates if the model should be timestamped.
     *
     * @var bool
     */
    public $timestamps = false;

    /**
     * Get the performances for the Athelete post.
     *
     * @return HasMany
     */
    public function performances()
    {
        return $this->hasMany('App\EloquentModels\Performance', 'athlete_id');
    }
}

class Performance extends Model
{
    /**
     * The table associated with the model.
     *
     * @var string
     */
    protected $table = 'performances';

    /**
     * The primary key associated with the table.
     *
     * @var string
     */
    protected $primaryKey = 'id';

    /**
     * Indicates if the model should be timestamped.
     *
     * @var bool
     */
    public $timestamps = false;
}

Answer 1

如果您使用的是原始 SQL，只需使用 GROUP BY 为每个运动员执行 MAX 即可。

SELECT athletes.*, MAX(performance) AS personal_best
FROM athletes
INNER JOIN performances ON athletes.id = performances.athlete_id AND performances.event_id = 1
GROUP BY athletes.id
ORDER BY personal_best DESC
LIMIT 0, 100

Laravel 查询构建器：

DB::table('athletes')
    ->join('performances', 'athletes.id', '=', 'performances.athlete_id')
    ->where('performances.event_id', '=', 1)
    ->groupBy('athletes.id')
    ->orderBy('personal_best', 'desc')
    ->select('athletes.*',DB::raw('MAX(performance) AS personal_best')
    ->limit(100);

Doc 说我们可以使用max(personal_best)，但不确定如何将它与 group by 一起使用。

恐怕您无法避免在查询生成器中使用DB::raw，但您可以使用eloquent model，正如Shaielndra Gupta 所回答的那样。

为此，您可以创建模型和关系。

1. Create Model:
php artisan make:model Athelete
php artisan make:model Performance

2. Create relationship between Athelete and Perforamnce.

Update Athelete.php 

    /**
     * Get the performances for the Athelete post.
     */
    public function performances()
    {
        return $this->hasMany('App\Performance');
    }

3. Get data(didn't verify by myself)
$data = Athelete::with('performances',function ($query) use ($eventId){
    $query->max('performance')
    $query->where('event_id',$eventId)
    $query->orderBy('performance');
})->get();

参考：

• Laravel Model
• Laravel Relationship

Answer 2

你可以像下面这样使用。

$sql1 = "(
         SELECT performance
         FROM performances
         WHERE athletes.id = performances.athlete_id AND performances.event_id = 1
         ORDER BY performance DESC
         LIMIT 0,1
     ) AS personal_best";

$sql2 = "SELECT athletes.*,$sql1          
FROM athletes
ORDER BY personal_best DESC
Limit 0, 100";

$result = DB::select($sql2);

Answer 3

在database.php 创建一个新连接，例如 mysql_dev 用于开发参数。

DB::connection('mysql_dev')->table('athletes')
    ->leftJoin('performances','athletes.id','performances.athlete_id')
    ->where('performances.event_id',1)
    ->groupBy('athletes.id')
    ->orderByDesc('personal_best')
    ->select('athletes.*',DB::raw('MAX(performances.performance) AS personal_best')
    ->paginate(100);

尝试这样不生，

DB::connection('mysql_dev')->table('athletes')
    ->leftJoin('performances','athletes.id','performances.athlete_id')
    ->where('performances.event_id',1)
    ->groupBy('athletes.id')
    ->orderByDesc('performances.performance')
    ->select('athletes.*','performances.performance'
    ->paginate(100);

Answer 4

你可以像这样使用 Eloquent ORM

$data = Athelete::with('performances',function ($query) use ($eventId){
    $query->max('performance')
    $query->where('event_id',$eventId)
    $query->orderBy('performance');
})->get()