在 Node.js Sequelize 中对连接表执行关联

Question

在 Postgres DB 上使用 Node.js Sequelize。我有以下三个表：Groups、Applications 和一个用于映射关系 GroupApplication 的连接表。 GroupApplication 使用 id 作为外键。当我在 sequelize 的 GroupApplication 表上查找所有内容时，我希望将各个组和应用程序的“名称”字段加入到各个表中。所以我想加入

Groups                            Applications    

| id| name     | description |       | id| name   | description |
| --|:--------:| -----------:|       | --|:------:| -----------:|
| 1 | admin    | First Group |       | 1 | typer  | Types       |
| 2 | primary  | Second Group|       | 2 | tester | Tests       |
| 3 | secondary| Third Group |       | 3 | zestrer| Zests       |


GroupApplications
| id| groups_id | application_id |
| --|:---------:| --------------:|
| 1 | 1         | 1              | 
| 2 | 1         | 2              |
| 3 | 1         | 3              |
| 4 | 2         | 2              |
| 5 | 2         | 3              |
| 6 | 3         | 2              |

The resulting join:

GroupApplications
| id|groups_id|group_name|application_id|application_name|
| --|:-------:|:--------:|:------------:|---------------:|
| 1 | 1       | admin    |1             |typer           |    
| 2 | 1       | admin    |2             |tester          |
| 3 | 1       | admin    |3             |zester          |
| 4 | 2       | primary  |2             |tester          |
| 5 | 2       | primary  |3             |zester          |
| 6 | 3       | secondary|2             |tester          |

我有以下文件：

groups.js       

module.exports = function (sequelize, DataTypes) {
  var Groups = sequelize.define('Groups', {
    id: {
      type: DataTypes.INTEGER,
      autoIncrement: true,
      primaryKey: true
    },
      name: {
      type: DataTypes.STRING,
      allowNull: false,
      unique: true
    }
  }, {
    timestamps: false,
    tableName: 'groups',
  });

  Groups.associate = function(models) {
    Groups.belongsToMany(models.GroupApplication, { through: 'group_application', foreignKey: 'group_id' });
  };

return Groups;
};


applications.js       

module.exports = function (sequelize, DataTypes) {
  var Applications = sequelize.define('Applications', {
    id: {
      type: DataTypes.INTEGER,
      autoIncrement: true,
      primaryKey: true
    },
      name: {
      type: DataTypes.STRING,
      allowNull: false,
      unique: true
    }
  }, {
    timestamps: false,
    tableName: 'groups',
  });

  Applications.associate = function(models) {
    Applications.belongsToMany(models.GroupApplication, { through: 'group_application', foreignKey: 'application_id' });
  };

return Applications;
};

group-application.js

module.exports = function (sequelize, DataTypes) {
  let GroupApplication = sequelize.define('GroupApplication', {
    group_id: {
      type: DataTypes.INTEGER,
      allowNull: false,
      primaryKey: true
    },
    application_id: {
      type: DataTypes.INTEGER,
      allowNull: false,
      primaryKey: true
    }
  }, {
    timestamps: false,
    tableName: 'group_application',
  });

  return GroupApplication;
};

Answer 1

您不需要定义GroupApplication，它会被推断出来，foreignKey 也是如此。关系应该在Group 和Application 之间（单数更好，把它想象成一个对象模型，你有一个Instance 和一个Application Model），但要加入through group_application桌子。完成此操作后，您可以将 include 每个 Models 放入另一个查询中。

请注意，我没有测试过这段代码。

group.js

module.exports = function (sequelize, DataTypes) {
  var Group = sequelize.define('Group', 
    {
      name: {
        type: DataTypes.STRING,
        allowNull: false,
        unique: true
      },
    },
    {
      tableName: 'group',
      timestamps: false,
      underscored: true,
    }
  );

  Group.associate = function(models) {
    Group.belongsToMany(models.Application, {
      as: 'applications',           // <-- alias here
      through: 'group_application',
    });
  };

  return Group;
};

application.js

module.exports = function (sequelize, DataTypes) {
  var Application = sequelize.define('Application',
    {
      name: {
        type: DataTypes.STRING,
        allowNull: false,
        unique: true
      },
    },
    {
      tableName: 'application',
      timestamps: false,
      underscored: true,
    }
  );

  Application.associate = function(models) {
    Application.belongsToMany(models.Group, {
      as: 'groups',           // <-- alias here
      through: 'group_application',
    });
  };

  return Application;
};

example.js

// return all Groups and their Applications
const groupsToApplications = await Group.findAll({
  include: [
    {
      model: Application,
      as: 'applications',
      through: 'group_application',
    },
  ],
});

// return all Applications and their Groups
const applicationsToGroups = await Application.findAll({
  include: [
    {
      model: Group,
      as: 'groups',
      through: 'group_application',
    },
  ],
});