使 SELECT 子查询 COUNT 个订阅者的总订阅者

Question

我正在尝试创建一个查询来计算一个订阅者的订阅者总数。目前看起来像这样：

await this.queryInstance.query(
'SELECT all_users_subbed_to.* , (SELECT COUNT(??????)) AS subscribers_sub_count
FROM 
 (SELECT publisher_id, subscriber_id, u2.username 
 AS username, u2.user_photo AS user_photo 
 FROM subscribers s 
 INNER JOIN users u 
 ON (u.id = s.subscriber_id) 
 INNER JOIN users u2 ON (u2.id = s.publisher_id) 
 WHERE subscriber_id = () 
 LIMIT 20 
 OFFSET ()) 
AS all_users_subbed_to;'
,
 [currentUserId = 80, offset]   
 );

FROM 子句又名 all_users_subbed_to 工作正常并显示当前用户拥有的所有订阅者。数据返回如下：

"subscribedToCurrentUser": [
        {
            "publisher_id": 84,
            "subscriber_id": 80,
            "username": "supercoookie",
            "user_photo": "profile-pic-for-supercoookie.jpeg"
        },
        {
            "publisher_id": 88,
            "subscriber_id": 80,
            "username": "GERPAL1",
            "user_photo": "profile-pic-for-GERPAL1.jpeg"
        }
    ]

我遇到的问题是获取这些订阅者列表的订阅者总数。我需要使用订阅者 publisher_id 即 all_users_subbed_to.publisher_id 并从订阅者 table 获取他们的订阅总数（使用 COUNT）。我想创建一个名为 have subscribers_sub_count 的新列，其中包含该总数。有任何想法吗？它应该是这样的：

"subscribedToCurrentUser": [
        {
            "publisher_id": 84,
            "subscriber_id": 80,
            "username": "supercoookie",
            "user_photo": "profile-pic-for-supercoookie.jpeg",
            "subscribers_sub_count": 3
        },
        {
            "publisher_id": 88,
            "subscriber_id": 80,
            "username": "GERPAL1",
            "user_photo": "profile-pic-for-GERPAL1.jpeg",
            "subscribers_sub_count": 70
        }
    ]

订阅者 table 看起来像这样：

Answer 1

await this.queryInstance.query(
'SELECT all_users_subbed_to.*, COUNT(all_users_subbed_to.id) AS subscribers_sub_count
FROM 
 (SELECT publisher_id, subscriber_id, u2.username 
 AS username, u2.user_photo AS user_photo 
 FROM subscribers s 
 INNER JOIN users u 
 ON (u.id = s.subscriber_id) 
 INNER JOIN users u2 ON (u2.id = s.publisher_id) 
 WHERE subscriber_id = () 
 LIMIT 20 
 OFFSET ()) 
AS all_users_subbed_to;'
,
 [currentUserId = 80, offset]   
 );

Answer 2

已修复。它只需要一个使用来自 all_users_subbed_to

的数据的 WHERE 子句

await this.queryInstance.query(
'SELECT all_users_subbed_to.* , 
(SELECT COUNT(*) FROM subscribers s2 WHERE s2.publisher_id = all_users_subbed_to.publisher_id) AS subscribers_sub_count AS subscribers_sub_count
FROM 
 (SELECT publisher_id, subscriber_id, u2.username 
 AS username, u2.user_photo AS user_photo 
 FROM subscribers s 
 INNER JOIN users u 
 ON (u.id = s.subscriber_id) 
 INNER JOIN users u2 ON (u2.id = s.publisher_id) 
 WHERE subscriber_id = () 
 LIMIT 20 
 OFFSET ()) 
AS all_users_subbed_to;'
,
 [currentUserId = 80, offset]   
 );

使 SELECT 子查询 COUNT 个订阅者的总订阅者

Make SELECT subquery COUNT the total subscribers of a subscriber

sql

postgresql

node-postgres