如何在NodeJS Sequelize中通过查询对组进行计数 [英] How to count a group by query in NodeJS Sequelize

问题描述

在Rails中，我可以执行一个简单的ORM查询，以了解模型的点赞次数：

In Rails I can perform a simple ORM query for the number of Likes a model has:

    @records = Model
        .select( 'model.*' )
        .select( 'count(likes.*) as likes_count' )
        .joins( 'LEFT JOIN likes ON model.id = likes.model_id' )
        .group( 'model.id' )

这将生成查询：

SELECT  models.*, count(likes.*) as likes_count
FROM "models" JOIN likes ON models.id = likes.model_id
GROUP BY models.id

在Node Sequelize中，任何尝试做某事的尝试类似的失败：

In Node Sequelize, any attempt at doing something similar fails:

return Model.findAll({
    group: [ '"Model".id' ],
    attributes: ['id', [Sequelize.fn('count', Sequelize.col('"Likes".id')), 'likes_count']],
    include: [{ attributes: [], model: Like }],
});

这将生成查询：

SELECT
    Model.id,
    count(Likes.id) AS likes_count,
    Likes.id AS Likes.id           # Bad!
FROM Models AS Model
LEFT OUTER JOIN Likes
    AS Likes
    ON Model.id = Likes.model_id
GROUP BY Model.id;

哪个会生成错误：

column "Likes.id" must appear in the GROUP BY clause or be used in an aggregate function

中使用

错误地选择了likes.id，我不知道为什么，也不知道如何摆脱它。

It's erroneously selecting likes.id, and I have no idea why, nor how to get rid of it.

推荐答案

此sequelize github问题看起来完全像您的情况：

This sequelize github issue looks totally like your case:

User.findAll({
  attributes: ['User.*', 'Post.*', [sequelize.fn('COUNT', 'Post.id'), 'PostCount']],
  include: [Post]
});

这篇关于如何在NodeJS Sequelize中通过查询对组进行计数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！