Postgres - 采用 JSON 创建的最伟大的列

Question

我在 Postgres 数据库中有一个 JSON 列，其中包含星期几的键和该日期的访问值。我想获取最大天数并将其添加为一周中所有天的值旁边的列。

我有以下我认为可以做到的查询。但我目前收到错误“列'星期一'不存在”

我从 JSON 中提取星期一后，为什么不存在星期一？内部查询工作正常，并按我的预期返回所有日期和相应的值（星期一、星期二、星期三、星期四、星期五的列）。我认为查询这些列并获得最大的列会相对容易。

SELECT Monday, Tuesday, Wednesday, Thursday, Friday,
GREATEST(Monday, Tuesday, Wednesday, Thursday, Friday) as MaxDay
FROM "VisitData"
WHERE
    (SELECT 
        popularity_by_day ->> 'Monday' AS Monday,
        popularity_by_day ->> 'Tuesday' AS Tuesday,
        popularity_by_day ->> 'Wednesday' AS Wednesday,
        popularity_by_day ->> 'Thursday' AS Thursday,
        popularity_by_day ->> 'Friday' AS Friday
    FROM "VisitData")

更新：

我现在在别名子查询之后有这个查询：

    SELECT Monday, Tuesday, Wednesday, Thursday, Friday,
    GREATEST(Monday, Tuesday, Wednesday, Thursday, Friday) as MaxDay
    FROM
        (SELECT 
            popularity_by_day ->> 'Monday' AS Monday,
            popularity_by_day ->> 'Tuesday' AS Tuesday,
            popularity_by_day ->> 'Wednesday' AS Wednesday,
            popularity_by_day ->> 'Thursday' AS Thursday,
            popularity_by_day ->> 'Friday' AS Friday
    FROM "VisitData") AS visits
    ```

This gives me the structure of the output im expecting but the results are inconsistent.

For example row 1 in the result
Monday = 5
Tuesday = 89
Wednesday = 95
Thursday = 120
Friday = 102
MaxDay = 95  (why not 120)

And for row 2
Monday = 329
Tuesday = 350
Wednesday = 439
Thursday = 397
Friday = 314
MaxDay = 439 (This is correct)

Answer 1

我想你想要一个横向连接：

SELECT v.Monday, v.Tuesday, v.Wednesday, v.Thursday, v.Friday,
       GREATEST(v.Monday, v.Tuesday, v.Wednesday, v.Thursday, v.Friday) as MaxDay
FROM "VisitData" vd CROSS JOIN LATERAL
     (SELECT vd.popularity_by_day ->> 'Monday' AS Monday,
             vd.popularity_by_day ->> 'Tuesday' AS Tuesday,
             vd.popularity_by_day ->> 'Wednesday' AS Wednesday,
             vd.popularity_by_day ->> 'Thursday' AS Thursday,
             vd.popularity_by_day ->> 'Friday' AS Friday
     ) v;