return 加入 table 但仅按主要 table id 分组

Question

我正在尝试 return 连接 4 个 table，但按 "commentcount" 对它们进行分组。但是我一直收到一个错误，告诉我将每个 table 的 'id' 添加到 GROUP BY 子句中。但是这样做会为每个 "commentcount" 给出“1” tables:

用户
配置文件（加入用户（有 user_id 列））
帖子（加入用户（有 user_id 列））
评论（加入帖子和用户（有 user_id 和 post_id 列））

这是我的查询：

SELECT 
    "Post".*, 
    COUNT(*) AS "CommentCount", 
    "PostComments"."id" AS "PostComments.id", 
    "User"."id" AS "User.id", 
    "User"."email" AS "User.email", 
    "User"."password" AS "User.password",  
    "User.Profile"."id" AS "User.Profile.id", 
    "User.Profile"."user_id" AS "User.Profile.user_id", 
    "User.Profile"."username" AS "User.Profile.username", 
    "User.Profile"."gender" AS "User.Profile.gender"
FROM
    "posts" AS "Post" 
LEFT OUTER JOIN 
    "post_comments" AS "PostComments" 
       ON     "Post"."id" = "PostComments"."post_id" 
          AND "PostComments"."deleted_at" IS NULL 
LEFT OUTER JOIN 
    "users" AS "User" 
       ON     "Post"."user_id" = "User"."id" 
          AND "User"."deleted_at" IS NULL 
LEFT OUTER JOIN 
    "profiles" AS "User.Profile" 
       ON  "User"."id" = "User.Profile"."user_id" 
WHERE "Post"."deleted_at" IS NULL
GROUP BY 
    "Post"."id";

我收到错误 column "User.id" must appear in the GROUP BY clause or be used in an aggregate function 但是当我添加它时，columncount 是错误的。

*如何按 Post.id 列分组并仍然从联接 table 中获取相应的数据？ *

N.B。一旦我弄明白了，我想将正确的查询转换为 sequelize.js，所以如果有人碰巧知道如何使用 sequelize 来完成它，我将非常欢迎 :)

Answer 1

我希望此查询给出每个 post 的评论数。

select "post_id", count(*) as num_comments
from "PostComments"
group by "post_id";

现在，无论您的其余查询做什么，您都可以从上面的查询加入 "post_id"。按照这些思路应该可以工作。

select ..., comment_count.num_comments
from ...
-- other joins go here . . .
left outer join (select "post_id", count(*) as num_comments
                 from "PostComments"
                 group by "post_id") comment_count
    on "Post"."id" = comment_count.post_id
where "Post"."deleted_at" is null;

return 加入 table 但仅按主要 table id 分组

return join table but group by only main table id

postgresql

sequelize.js