sequelize count associated table 行

Question

使用 sequelize 和 mySQL，我有两个表：User 和 Post。

两个表之间的关系是M : N

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

我想要的是 post 整个点赞者 ID 和点赞者总数。

我知道how to get whole likers是这样的

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
    }
  ]
}

而且，我也知道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
    }
  ]
}

但是，我不知道如何同时获得它们。当我同时使用它们时检查结果。

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

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

只显示1个赞(id: 13) 它必须显示另一个 liker(id: 16).

有什么问题？

Answer 1

它只显示一个，因为 COUNT 是一个聚合函数，它将记录分组以对它们进行计数。因此，获得两者的唯一方法 - 使用子查询计算联结 table 中的记录，同时获取 M:N 关系另一端的记录。

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: [] },
  }]
})

sequelize count associated table 行

sequelize count associated table rows

mysql

node.js

sequelize.js