小编dhi*_*eth的帖子

我正在尝试实现以下查询来处理SQLAlchemy中的嵌套集(请参阅此处).我正在努力的是如何在最后一个子句depth中的主SELECT查询(这取决于子SELECT查询)中使用带标签的计算HAVING.

SELECT node.name, (COUNT(parent.name) - (sub_tree.depth + 1)) AS depth
FROM nested_category AS node,
    nested_category AS parent,
    nested_category AS sub_parent,
    (
            SELECT node.name, (COUNT(parent.name) - 1) AS depth
            FROM nested_category AS node,
                    nested_category AS parent
            WHERE node.lft BETWEEN parent.lft AND parent.rgt
                    AND node.name = 'PORTABLE ELECTRONICS'
            GROUP BY node.name
            ORDER BY node.lft
    )AS sub_tree
WHERE node.lft BETWEEN parent.lft AND parent.rgt
    AND node.lft BETWEEN sub_parent.lft AND sub_parent.rgt
    AND sub_parent.name = sub_tree.name …

我正在考虑按照数据透视表上定义的顺序显示asset属于 a 的 s列表。在这种情况下，该功能没有任何作用。不会引发错误，但无论如何它都会以相同的顺序返回集合数组。productorder_columnproduct_assetsortBy

以下是我目前列出的内容：

数据库：

    Schema::create('product_asset', function (Blueprint $table) {
        $table->integer('product_id')->unsigned()->index();
        $table->foreign('product_id')->references('id')->on('products')->onDelete('cascade');

        $table->integer('asset_id')->unsigned()->index();
        $table->foreign('asset_id')->references('id')->on('assets')->onDelete('cascade');

        $table->unsignedInteger('order_column')->nullable();
    });

模型：

/**
 * The assets that belong to the product.
 */
public function assets()
{
    return $this->belongsToMany('App\Asset', 'product_asset')->withPivot('order_column');
}

看法：

<ul>
    @foreach($resources->sortBy('pivot_order_column') as $resource)
        <li><a href="{{ $resource->url }}">{{ $resource->name }}</a></li>
    @endforeach
</ul>

我将非常感谢对此的任何帮助！提前致谢。

类似问题：

https://laravel.io/forum/04-17-2014-order-by-pivot-table-attribute-in-eloquent

Laravel 在多对多关系中按枢轴进行雄辩排序

我正在使用Pyramid框架并使用Deform包来呈现HTML表单,并给出了漏勺方案.我正在努力解决如何处理具有多对多关系的模式的问题.例如,我的s​​qlalchemy模型如下所示:

class Product(Base):
    """ The SQLAlchemy declarative model class for a Product object. """
    __tablename__ = 'products'

    id = Column(Integer, primary_key=True)
    name = Column(String(80), nullable=False)
    description = Column(String(2000), nullable=False)
    categories = relationship('Category', secondary=product_categories,
                               backref=backref('categories', lazy='dynamic'))


class Category(Base):                                                                                
    """ The SQLAlchemy declarative model class for a Category object. """                            
    __tablename__ = 'categories'

    id = Column(Integer, primary_key=True)                                                                                            
    name = Column(String(80), nullable=False)                                                                                                                                 
    products = relationship('Product', secondary=product_categories,                                 
                               backref=backref('products', lazy='dynamic'))


product_categories = Table('product_categories', Base.metadata,
    Column('products_id', Integer, ForeignKey('products.id')),
    Column('categories_id', Integer, ForeignKey('categories.id'))
)

如您所见,这是一个非常简单的模型,代表一个在线商店,其中一个产品可以属于一个或多个类别.在我的渲染形式中,我想有一个选择多个字段,我可以在其中选择几个不同的类别来放置产品.这是一个简单的漏勺模式:

def …

我有一个product与多对多关系的模型,product_categories如下所述:

class Product(Base):
    """ The SQLAlchemy declarative model class for a Product object. """
    __tablename__ = 'products'

    id = Column(Integer, primary_key=True)
    part_number = Column(String(10), nullable=False, unique=True)
    name = Column(String(80), nullable=False, unique=True)
    description = Column(String(2000), nullable=False)
    categories = relationship('Category', secondary=product_categories,
                               backref=backref('categories', lazy='dynamic'))


class Category(Base):
    """ The SQLAlchemy declarative model class for a Category object. """                        
    __tablename__ = 'categories'                                                                 

    id = Column(Integer, primary_key=True)
    lft = Column(Integer, nullable=False)
    rgt = Column(Integer, nullable=False)                                                        
    name = Column(String(80), nullable=False)                                                    
    description = Column(String(2000), …