如何实现多对多结局

Question

我有两个表：书籍和文章，它们之间有多对多的关系。联接表是BookArticles。

models / books.js

module.exports = function(sequelize, DataTypes) {
  return Food = sequelize.define("Book", {
    id: {
      type: DataTypes.INTEGER,
      primaryKey: true,
      allowNull: false,
      autoIncrement: true,
      unique: true
    }
  });
}

models / articles.js

module.exports = function(sequelize, DataTypes) {
  return Food = sequelize.define("Article", {
    id: {
      type: DataTypes.INTEGER,
      primaryKey: true,
      allowNull: false,
      autoIncrement: true,
      unique: true
    }
  });
}

models / bookArticles.js

module.exports = function(sequelize, DataTypes) {
  return Food = sequelize.define("BookArticles", {
    id: {
      type: DataTypes.INTEGER,
      primaryKey: true,
      allowNull: false,
      autoIncrement: true,
      unique: true
    },
   bookId: {
      type: DataTypes.INTEGER,
      references: 'Book',
      referencesKey: 'id',
      allowNull: false
    },
    ArticleId: {
      type: DataTypes.INTEGER,
      references: 'Article',
      referencesKey: 'id',
      allowNull: false
    },
  });
}

和models / index.js

m.BookArticles.belongsTo(m.Book);
m.Book.hasMany(m.Article, {through: m.BookArticles});


m.BookArticles.belongsTo(m.Article);
m.Article.hasMany(m.Books, {through: m.BookArticles});

但我无法获得书籍文章

我怎么才能得到它 ？？

Answer 1

已针对Sequelize v2 / 3/4/5更新

通常，我认为问题在于我们对创建的表以及关联获得的方法感到困惑。

注意：定义foreignKey或交叉表名称是可选的。Sequelize自动创建它，但是对其进行定义，使编码人员可以读取模型并找出外键/交叉表名称是什么，而不用猜测或需要访问数据库。

TLDR；

O：O

// foreign key has to be defined on both sides.
Parent.hasOne(Child, {foreignKey: 'Parent_parentId'})
// "Parent_parentId" column will exist in the "belongsTo" table.
Child.belongsTo(Parent, {foreignKey: 'Parent_parentId'})

O：M

Parent.hasMany(Child, {foreignKey: 'Parent_parentId'})
Child.belongsTo(Parent, {foreignKey: 'Parent_parentId'})

N：M

Parent.belongsToMany(
    Child, 
    {
        // this can be string (model name) or a Sequelize Model Object Class
        // through is compulsory since v2
        through: 'Parent_Child',

        // GOTCHA
        // note that this is the Parent's Id, not Child. 
        foreignKey: 'Parent_parentId'
    }
)

/*
The above reads:
"Parents" belongs to many "Children", and is recorded in the "Parent_child" table, using "Parents"'s ID.
*/

Child.belongsToMany(
    Parent, 
    {
        through: 'Parent_Child',

        // GOTCHA
        // note that this is the Child's Id, not Parent.
        foreignKey: 'Child_childId'
    }
)

为什么要冗长的“ Parent_parentId”，而不仅仅是“
parentId”？这很明显表明它是属于“父母”的外键。在大多数情况下，可以使用更简洁的“ parentId”。*

关联为您提供2种功能：（1）渴望加载和（2）DAO方法：

1.包含（急切加载）

DB.Parent.findOne({ 
    where: { id: 1 },
    include: [ DB.Child ]
}).then(parent => {

    // you should get `parent.Child` as an array of children.

})

2. hasOne（），hasMany（）和belongsTo（）/ belongsToMany（）获得的方法

关联提供了数据访问对象（DAO）方法：

hasOne（）：

在设置中Parent.hasOne(Child)，可用于parentDAO实例的方法：

DB.Parent.findOne({ where: { id: 1 } }).then(parent => {

    // `parent` is the DAO
    // you can use any of the methods below:
    parent.getChild
    parent.setChild
    parent.addChild
    parent.createChild
    parent.removeChild
    parent.hasChild

})


#### hasMany():

In setting a `Parent.hasMany(Child)`, methods available to `parent` DAO instance:

```js
parent.getChildren,
parent.setChildren,
parent.addChild,
parent.addChildren,
parent.createChild,
parent.removeChild,
parent.hasChild,
parent.hasChildren

归属于（）/ belongsToMany：

在设置中Child.belongsTo(Parent)，可用于childDAO实例的方法：

child.getParent,
child.setParent,
child.createParent

//belongsToMany
child.getParents,
child.setParents,
child.createParents

您也可以有多个关系

亲生父母/子女

// a parent can have many children
Parent.belongsToMany(Child, {
    as: 'Natural',
    through: 'Parent_Child',
    foreignKey: 'Parent_parentId'
})
// a child must at least have 2 parents (natural mother and father)
Child.belongsToMany(Parent, {
    as: 'Natural',
    through: 'Parent_Child',
    foreignKey: 'Child_childId'
})

养育父母/子女

Parent.belongsToMany(Child, {
    as: 'Foster',
    through: 'Parent_Child',
    foreignKey: 'Parent_parentId'
})

Child.belongsToMany(Parent, {
    as: 'Foster',
    through: 'Parent_Child',
    foreignKey: 'Child_childId'
});

上面将Parent_Child使用NaturalId和创建交叉表FosterId。