返回連接表，但只由主表ID編號

我想返回4個表的連接，但通過「commentcount」將它們分組。但是我保持gettng一個錯誤，告訴我將每個表的'id'添加到GROUP BY子句中。但這樣做提供了每個「commentcount」表 '1'：返回連接表，但只由主表ID編號

用戶
配置文件（連接到用戶（已經user_id列））
帖子（連接到用戶（已經user_id列））
評論（加入到崗位和用戶（已user_id說明和POST_ID列））

這裏是我的查詢：

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";

我收到錯誤column "User.id" must appear in the GROUP BY clause or be used in an aggregate function但是當我補充說columncount是錯誤的。

*如何按Post.id列進行分組，並仍然從連接表中獲取相應的數據？ *

N.B.我想將正確的查詢轉換爲sequelize.js，一旦我找到了它，所以如果有人碰巧知道如何使用sequelize做到這一點，我會更歡迎:)

來源

2015-01-14 DBrowne

Postgresql does not工作爲mysql，讓您添加任何字段與聚合函數whitout抱怨。如果您使用聚合，例如'count（*）'你應該在'group by'語句中添加你選擇的所有字段。 –

CREATE TABLE語句是描述表格的最佳方式。將這些粘貼到您的問題中。 –

我' d期望這個查詢給出每個帖子的評論數量。

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

現在，無論查詢的其餘部分如何，您都可以通過上面的查詢加入「post_id」。沿着這些線應該工作。

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;

來源

2015-01-14 03:37:15

即使我聲明'LEFT OUTER JOIN'post_comments「AS」PostComments「'，在子查詢中，我必須將'PostComments''替換爲'from'from'post_comments」'。之後，它完美的工作！謝謝。 – DBrowne

返回連接表，但只由主表ID編號

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