Python：将PostgreSQL查询结果检索为格式化的JSON值

我正在使用包含几个表的postgres数据库.目标是从获得的查询结果中检索格式化的JSON.我创建了这个python脚本从表(测试用例)中获取数据集,以便操作查询结果：

import psycopg2
import json
from time import sleep
from config import config

def main():
    conn = None
    try:
        params = config()
        conn = psycopg2.connect(**params)
        cur = conn.cursor()
        cur.execute("select * from location")
        row = cur.fetchone()

        while row is not None:
            print(row)
            #do field rename, merge(log, lat) and obtained JSON here
            sleep(0.3)
            row = cur.fetchone()

        cur.close()
    except (Exception, psycopg2.DatabaseError) as error:
        print(error)
    finally:
        if conn is not None:
            conn.close()

if __name__ == '__main__':
    main()

为了使我的问题清楚,我在这里制作了一个简化的场景,用3个表格表示手头的任务,如下所示.

environment
╔════════╦═══════════╦══════╦══════╗
║ env_id ║ placem_id ║ humd ║ wind ║
╠════════╬═══════════╬══════╬══════╣
║     104║        4  ║   48 ║  119 ║
║     68 ║        9  ║   39 ║  141 ║
╚════════╩═══════════╩══════╩══════╝

placement
╔═══════════╦════════╦═══════════════╦══════════════════════════╗
║ placem_id ║ loc_id ║  description  ║           date           ║
╠═══════════╬════════╬═══════════════╬══════════════════════════╣
║         4 ║     64 ║ description_1 ║ 2019-03-12T20:40:35.967Z ║
║         7 ║      5 ║ description_2 ║ 2019-03-12T20:56:51.319Z ║
╚═══════════╩════════╩═══════════════╩══════════════════════════╝

location
╔════════╦═══════════╦═══════════╦════════════════════╗
║ loc_id ║    log    ║    lat    ║      address       ║
╠════════╬═══════════╬═══════════╬════════════════════╣
║     64 ║ 13.3986   ║ 52.5547   ║ Bosebrucke Einkauf ║
║     71 ║ 21.150122 ║ -6.607044 ║ Charlotte Court    ║
╚════════╩═══════════╩═══════════╩════════════════════╝

这就是我想要实现的目标：

>从数据库中检索记录
>在JSON名称/值中适当地重命名一些字段(例如,humd成为relativeHumidity和windto windSpeed
>将log和lat字段合并为单个JSON值,如坐标[log,lat]

因此返回的JSON采用以下形式：

{
    "relativeHumidity": 48,
    "windSpeed": 119,
    "address": "Bosebrucke Einkauf",
    "location": {
        "coordinates": [13.3986, 52.5547]
    }
}

虽然这个问题可能看似重复,但我尝试了许多类似问题的建议,例如here,但这些都没有实际起作用.

那里的任何人都可以提供指南吗？

解决方法:

我认为使用functions-json应该相对容易：

select
    json_agg(to_json(d))
from (
    select
        e.humd as "relativeHumidity",
        e.wind as "windSpeed",
        l.address,
        json_build_object(
            'coordinates',
            json_build_array(l.log, l.lat)
        ) as location
    from environment as e
        inner join placement as p on
            p.placem_id = e.placem_id
        inner join location as l on
            l.loc_id = p.loc_id
) as d

db<>fiddle demo