使用子查询更新为所有记录设置相同的值

Question

我试图根据列的值（updated_at）计算每条记录的权重。当我运行以下查询：

UPDATE buyers 
SET weight = RankedRecords.rank/(RankedRecords.count + 1.0) 
FROM (
    SELECT 
    id, 
    RANK() OVER (
     PARTITION BY board_list_id ORDER BY 'updated_at' ASC 
    ) AS rank, 
    COUNT(id) OVER (PARTITION BY board_list_id) AS count 
    FROM buyers 
) RankedRecords 
WHERE buyers.id = RankedRecords.id 

与同board_list_id所有记录得到他们weight更新为相同的值。虽然我预计所有weight值都会有所不同，并取决于排名。
只运行子查询会产生正确的结果（每个记录具有不同的等级）。但更新不能按预期工作。
我应该改变什么？

Answer 1

在查询中有一个非常微妙的错误。试试这个：

UPDATE 
    buyers 
SET 
    weight = RankedRecords.rank/(RankedRecords.count + 1.0) 
FROM 
(
    SELECT 
     id, 
     rank() OVER (PARTITION BY board_list_id ORDER BY updated_at ASC) AS rank, 
     count(id) OVER (PARTITION BY board_list_id) AS count 
    FROM buyers 
) RankedRecords 
WHERE 
    buyers.id = RankedRecords.id ; 

你的痘痘错误：ORDER BY 'updated_at'只是ORDER BY 'constant-text'。如果要参考该列，请使用"updated_at"（与双引号）或updated_at（没有它们，因为您的列的名称只是ASCII小写字符）。

与尝试：

CREATE TABLE buyers 
(
    id integer not null primary key, 
    board_list_id integer not null, 
    updated_at timestamp not null default now(), 
    weight double precision 
) ; 
INSERT INTO buyers (id, board_list_id, updated_at) 
VALUES 
    (1, 1, '2017-01-09'), 
    (2, 1, '2017-01-10'), 
    (3, 1, '2017-01-11'), 
    (4, 1, '2017-01-12'), 
    (5, 2, '2017-01-09'), 
    (6, 2, '2017-01-10'), 
    (7, 2, '2017-01-11'), 
    (8, 1, '2017-01-12') ; 

以前更新的结果（与一名选举*子句）将是：

|----+---------------+---------------------+--------+----+------+-------| 
| id | board_list_id |  updated_at  | weight | id | rank | count | 
|----+---------------+---------------------+--------+----+------+-------| 
| 1 |  1  | 2017-01-09 00:00:00 | 0.1667 | 1 | 1 | 5 | 
|----+---------------+---------------------+--------+----+------+-------| 
| 2 |  1  | 2017-01-10 00:00:00 | 0.3333 | 2 | 2 | 5 | 
|----+---------------+---------------------+--------+----+------+-------| 
| 3 |  1  | 2017-01-11 00:00:00 | 0.5 | 3 | 3 | 5 | 
|----+---------------+---------------------+--------+----+------+-------| 
| 8 |  1  | 2017-01-12 00:00:00 | 0.6667 | 8 | 4 | 5 | 
|----+---------------+---------------------+--------+----+------+-------| 
| 4 |  1  | 2017-01-12 00:00:00 | 0.6667 | 4 | 4 | 5 | 
|----+---------------+---------------------+--------+----+------+-------| 
| 5 |  2  | 2017-01-09 00:00:00 | 0.25 | 5 | 1 | 3 | 
|----+---------------+---------------------+--------+----+------+-------| 
| 6 |  2  | 2017-01-10 00:00:00 | 0.5 | 6 | 2 | 3 | 
|----+---------------+---------------------+--------+----+------+-------| 
| 7 |  2  | 2017-01-11 00:00:00 | 0.75 | 7 | 3 | 3 | 
|----+---------------+---------------------+--------+----+------+-------|