Good evening.

I have a database with the following N:N association:

-> BlogPost.belogsToMany(Category through: PostsCategories)

-> Category.belongsToMany(BlogPost through: PostsCategories)

PostsCategories being the junction table's model.

On the process of inserting one BlogPost to the database, I have to catalog in which categories does it fall under on the junction table. So following some examples on the documentation I came up with:

const blogPost = await BlogPost.create({ title, content, userId });
await blogPost.addCategories(categoriesList);

So far so good, but there was an error. Basically Sequelize is inverting the order on the columns/values when writing the query. If I add

blogPost: { id: 3, categories: [1, 2] }

it produces this query:

"'INSERT INTO `PostsCategories` (`categoryId`,`postId`) VALUES (3,1),(3,2);'"

It's inverted and I've tried a gazillion things and it doesn't work. :(

Any thoughts on this?

Thanks!

EDIT: MY MODELS

module.exports = (sequelize, DataTypes) => {
  const Category = sequelize.define('Category', {
    name: DataTypes.STRING,
  },
  { tableName: 'Categories', timestamps: false });

  Category.associate = (models) => {
    const { BlogPost, PostsCategories } = models;

    Category.belongsToMany(
      BlogPost, { through: PostsCategories, foreignKey: 'postId', as: 'blogPosts' },
    );
  };

  return Category;
};

module.exports = (sequelize, DataTypes) => {
  const BlogPost = sequelize.define('BlogPost', {
    title: DataTypes.STRING,
    content: DataTypes.STRING,
    userId: DataTypes.INTEGER,
  },
  { tableName: 'BlogPosts', timestamps: true, createdAt: 'published', updatedAt: 'updated' });

  BlogPost.associate = (models) => {
    const { User, PostsCategories, Category } = models;

    BlogPost.belongsToMany(
      Category, { through: PostsCategories, foreignKey: 'categoryId', as: 'categories' },
    );

    BlogPost.belongsTo(User, { foreignKey: 'userId', as: 'user' });
  };

  return BlogPost;
};

module.exports = (sequelize, _DataTypes) => {
  const PostsCategories = sequelize.define('PostsCategories', 
  {},
  { timestamps: false, tableName: 'PostsCategories' });

  return PostsCategories;
};