带有 Sequelize many to many 的额外列答案

【问题标题】：extra columns with Sequelize many to many带有 Sequelize many to many 的额外列
【发布时间】：2020-06-25 17:07:04
【问题描述】：

我想知道如何从链接器表中获取额外的列。

目前我有 3 张桌子：

Courses : id, title, description,
Sections: id, title, description,
CoursesSections : id, fk_course_id, fk_section_id, position

我尝试使用这个来获取课程，但我不明白如何从链接器表中获取“位置”：

db.Course.findOne({
    where: {
        id: 1,
    },
    include: [
        {
            model: db.Section,
            as: "Section",
            through: {
                attributes: ["position"],
            },
        },
    ],
    order: [[Sequelize.literal("position"), "ASC"]],
}).then((response) => {
    console.log(response.dataValues.position) // <= undefined
    console.log(response.dataValues.Section.position) // <= <= undefined
    return response.dataValues.Section // <= get without "position" field
})

课程模式：

Course.associate = (models) => {
    models.Course.belongsToMany(models.Section, {
        as: "Section",
        through: "CourseSection",
        foreignKey: "fk_course_id",
        otherKey: "fk_section_id",
    })
}

截面模型：

Section.associate = (models) => {
    models.Section.belongsToMany(models.Course, {
        as: "Course",
        through: "CourseSection",
        foreignKey: "fk_section_id",
        otherKey: "fk_course_id",
    })
}

【问题讨论】：

标签： node.js sequelize.js

【解决方案1】：

创建一个 CourseSection 模型：

CourseSection.associate = (models) => {
    models.CourseSection.belongsToMany(models.Course, {
        through: "CoursesSections",
        foreignKey: "fk_course_id",
    })
    models.CourseSection.belongsToMany(models.Section, {
        through: "CoursesSections",
        foreignKey: "fk_section_id",
    })
}

将 CourseSection 与 Course 和 Section 相关联，如下所示：

Course.associate = (models) => {
    models.Course.belongsToMany(models.Section, {
        as: "Section",
        through: models.CourseSection,
        foreignKey: "fk_course_id",
        otherKey: "fk_section_id",
    })
}

Section.associate = (models) => {
    models.Section.belongsToMany(models.Course, {
        as: "Course",
        through: models.CourseSection,
        foreignKey: "fk_section_id",
        otherKey: "fk_course_id",
    })
}

用这个获取位置字段：

const course = await db.Course.findOne({
    where: {
        id: parent.dataValues.id,
    },
    include: [
        {
            model: db.Section,
            as: "Section",
            through: {
                attributes: ["position"],
            },
        },
    ],
    order: [[Sequelize.literal("position"), "ASC"]],
})

course.Section.forEach((section) => {
    console.log(section.dataValues.coursessections.position)

    section.position = section.dataValues.coursessections.position
})

return course.dataValues.Section

【讨论】：

谢谢@Anatoly！我更新了你的帖子，做了一些修改！