在 Sequelize 迁移中创建关联 [英] Creating associations in Sequelize migration

问题描述

Node.js.续集 4.41.尝试通过另一个表制作具有多对多关系的 2 个模型.例如，使用 sequelize-cli 运行...

Nodejs. Sequelize 4.41. Try to make 2 models with relation many-to-many through another table. Running with sequelize-cli, for example...

sequelize model:generate --name Camera --attributes name:string,sn:string

这是模型

// Camera model

'use strict';

module.exports = (sequelize, DataTypes) => {
  const Сamera = sequelize.define('Сamera', {
    name: DataTypes.STRING,
    sn: DataTypes.STRING
  }, {});
  Сamera.associate = function(models) {
    // associations can be defined here
      Camera.belongsToMany(models.Relay, {through: 'CameraRelay'});
  };
  return Сamera;
};

和

// Relay model

'use strict';

module.exports = (sequelize, DataTypes) => {
  const Relay = sequelize.define('Relay', {
    name: DataTypes.STRING,
    sn: DataTypes.STRING,
    channel: DataTypes.INTEGER
  }, {});
  Relay.associate = function(models) {
    // associations can be defined here
      Relay.belongsToMany(models.Camera, {through: 'CameraRelay'});
  };
  return Relay;
};

在文档中有短语

Belongs-To-Many 关联用于连接具有多个目标的源.此外，目标还可以连接到多个源.

Belongs-To-Many associations are used to connect sources with multiple targets. Furthermore the targets can also have connections to multiple sources.

Project.belongsToMany(User, {through: 'UserProject'});User.belongsToMany(Project, {through: 'UserProject'});

这将使用等效的外键创建一个名为 UserProject 的新模型projectId 和 userId.

This will create a new model called UserProject with the equivalent foreign keys projectId and userId.

迁移是

// create-relay

'use strict';
module.exports = {
  up: (queryInterface, Sequelize) => {
    return queryInterface.createTable('Relays', {
      id: {
        allowNull: false,
        autoIncrement: true,
        primaryKey: true,
        type: Sequelize.INTEGER
      },
      name: {
        type: Sequelize.STRING
      },
      sn: {
        type: Sequelize.STRING
      },
      channel: {
        type: Sequelize.INTEGER
      },
      createdAt: {
        allowNull: false,
        type: Sequelize.DATE
      },
      updatedAt: {
        allowNull: false,
        type: Sequelize.DATE
      }
    });
  },
  down: (queryInterface, Sequelize) => {
    return queryInterface.dropTable('Relays');
  }
};

和

//create camera
'use strict';
module.exports = {
  up: (queryInterface, Sequelize) => {
    return queryInterface.createTable('Сameras', {
      id: {
        allowNull: false,
        autoIncrement: true,
        primaryKey: true,
        type: Sequelize.INTEGER
      },
      name: {
        type: Sequelize.STRING
      },
      sn: {
        type: Sequelize.STRING
      },
      createdAt: {
        allowNull: false,
        type: Sequelize.DATE
      },
      updatedAt: {
        allowNull: false,
        type: Sequelize.DATE
      }
    });
  },
  down: (queryInterface, Sequelize) => {
    return queryInterface.dropTable('Сameras');
  }
};

为什么它在我运行 migrate 时不创建模型 CameraRelay 并且不为同一个模型创建迁移?

Why it doesn't create model CameraRelay and doesn't create migration for same model when I running migrate?

推荐答案

我想误解是关于 sync 与 migration:您所指的文档的很大一部分，正在使用 sync 方法从模型开始创建所有表和关联.

I guess the misunderstanding is about sync vs migration: great part of documentation you are referring to, is using the sync method to create all tables and associations starting from models.

当您使用迁移时，您正在使用迁移文件创建数据库所有表/列/关联(在我看来，这是用于生产的更好方法).

When you are using migrations, you are creating db all of your table/columns/associations using migration files (and in my hopinion, this is a better way for something that is going to production).

要了解差异，只需查看您的相机型号与相机迁移文件:

To understand the difference, just look at your camera model vs your camera migration file:

• 模型只定义了name和sn属性
• 迁移文件当然有name 和sn，但它有id、createdAt 和>updatedAt 也是.

• the model has only name and sn properties defined
• the migration file has of course name and sn, but it has id, createdAt and updatedAt too.

迁移文件旨在以安全的方式更改您的数据库，允许您回滚到过去的任何时间点.

Migrations are file with the aim of change your db in a safe way, allowing you to rollback to any point in the past.

所以，回到你的问题，你必须:

So, back to your problem, you have to:

• 创建一个新的迁移文件来创建新的 CameraRelay 表，其中包含 Camera 和 Relay 表的外键
• 使用与 CameraRelay 表的一对多关系更新您当前的相机迁移文件
• 使用与 CameraRelay 表的一对多关系更新您当前的 Relay 迁移文件

CameraRelay 迁移示例:

CameraRelay migration example:

    'use strict';
    module.exports = {
      up: (queryInterface, Sequelize) => {
        return queryInterface.createTable('CameraRelays', {
          cameraId: {
            primaryKey: true,
            type: Sequelize.INTEGER,
            allowNull: false,
            references: {        
              model: 'Relay',
              key: 'id'
            }
          },
          relayId: {
            primaryKey: true,
            type: Sequelize.INTEGER,
            allowNull: false,
            references: {         
              model: 'Camera',
              key: 'id'
            }
          },
          createdAt: {
            allowNull: false,
            type: Sequelize.DATE
          },
          updatedAt: {
            allowNull: false,
            type: Sequelize.DATE
          }
        });
      },
      down: (queryInterface, Sequelize) => {
        return queryInterface.dropTable('CameraRelays');
      }
    };

这篇关于在 Sequelize 迁移中创建关联的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！