条件表连接

Question

我的 eloquent 模型中有以下范围，我想向它添加两个条件。我需要帮助。

public function scopeImages($query) {
    $query->join('images as i', function ($join) {
        $join->on('i.vessel_id', '=', 'vessel.id')
        ->where('i.sort', '=', 'min(i.sort)');
    })
    ->leftjoin('users', 'users.id', '=', 'vessel.user_id')
    ->select('vessel.*', 'i.image as image', 'users.name as brokername');
}

images 表有 featured 和 sort 列。我想选择返回结果中images.featured is 1 和min sort 所在的一行。如果没有images.featured=1，那么我想选择min of sort。

目前上述范围为每个vessel_id选择min sort的图像

Answer 1

你需要一个相关的子查询

https://dev.mysql.com/doc/refman/5.5/en/correlated-subqueries.html

    SELECT  v.*, 
(SELECT `image` FROM images WHERE vessel_id = v.id ORDER BY featured DESC, sort LIMIT 1) AS image
    FROM `vessel` AS v

@编辑 你可以试试这个：

public function scopeImages($query) {
    return $query
        ->leftjoin('users', 'users.id', '=', 'vessel.user_id')
        ->select(\DB::raw("vessel.*, (SELECT `image` FROM images WHERE vessel_id = vessel.id ORDER BY featured DESC, sort LIMIT 1) AS image, users.name as brokername"));
} 

Answer 2

如果您在 desc 中按特征（如果特征是布尔值）排序并在 asc 中排序，它将以最高优先级列出特征 1，然后从 min 到 max 列出排序。现在，如果你占据第一排，你会得到你想要的。

$query->join('images', 'images.vessel_id', '=', 'vessel.id')
        ->leftjoin('users', 'users.id' ,'=', 'vessel.user_id')
        ->select('vessel.*', 'images.image as image', 'users.name as brokername')
        ->orderBy('images.featured', 'DESC')
        ->orderBy('images.sort', 'ASC')
        ->take(1);