sequelize count associated table rows-CodePudding

Using sequelize and mySQL, I have two tables: User and Post.

Relation between two tables is M : N

db.User.belongsToMany(db.Post, { through: "Likes", as: "Liked" });
db.Post.belongsToMany(db.User, { through: "Likes", as: "Likers" });

What I want is getting post with whole likers id and count of whole likers.

I know how to get whole likers like this.

const post = await Post.findOne({
  where: { id: postId },
  attributes: ["id", "title", "imageUrl"],
  include: [{
    model: User,
    as: "Likers",
    attributes: ["id"],
    through: { attributes: [] },
  }]
})

// result
{
  "id": 36,
  "title": "test",
  "imageUrl": "하늘이_1644886996449.jpg",
  "Likers": [
    {
      "id": 13
    },
    {
      "id": 16
    }
  ]
}

And, I also know how to get count of whole likers.

const post = await Post.findOne({
  where: { id: postId },
  attributes: ["id", "title", "imageUrl"],
  include: [{
    model: User,
    as: "Likers",
    attributes: [[sequelize.fn("COUNT", "id"), "likersCount"]],
  }]
})

// result
{
  "id": 36,
  "title": "test",
  "imageUrl": "하늘이_1644886996449.jpg",
  "Likers": [
    {
      "likersCount": 2
    }
  ]
}

But, I don't know how to get both of them at once. Check the result when I use both of them.

{
  model: User,
  as: "Likers",
  attributes: ["id", [sequelize.fn("COUNT", "id"), "likersCount"]],
  through: { attributes: [] },
}

// result
"Likers": [
  {
    "id": 13,
    "likersCount": 2
  }
]

It only shows 1 liker(id: 13) It must show another liker(id: 16).

What is the problem?

CodePudding user response：

It shows only one because COUNT is an aggregating function and it groups records to count them. So the only way to get both - use a subquery to count records in a junction table while getting records on the other end of M:N relationship.

const post = await Post.findOne({
  where: { id: postId },
  attributes: ["id", "title", "imageUrl", 
  // you probably need to correct the table and fields names
  [Sequelize.literal('(SELECT COUNT(*) FROM Likes where Likes.postId=Post.id)'), 'LikeCount']],
  include: [{
    model: User,
    as: "Likers",
    attributes: ["id"],
    through: { attributes: [] },
  }]
})