Postgres 在 json 中找到唯一值

Question

我正在使用 Postgresql 并且有一个 table，id，sender::jsonb 和日期，如下所示：

id |                                      sender                                        | last login date                 
----+-----------------------------------------------------------------------------------+----------------------------------
  1 | {"firstName": "Ivan",    "lastName": "Ivanov",       "middleName": "Ivanovich", } | 2021-04-10 14:49:36.234504 +00:00   
  2 | {"firstName": "Ivan",    "lastName": "Ivanov",       "middleName": "Ivanovich", } | 2021-04-09 14:49:36.234504 +00:00 
  3 | {"firstName": "Ivan",    "lastName": "Ivanov",       "middleName": "Ivanovich", } | 2021-04-11 14:49:36.234504 +00:00 
  4 | {"firstName": "Nickolai","lastName": "Nickov",       "middleName": "Nikovich", }  | 2021-04-30 14:49:36.234504 +00:00 
  5 | {"firstName": "Nickolai","lastName": "Nickov",       "middleName": "Nikovich", }  | 2021-04-29 14:49:36.234504 +00:00 
  6 | {"firstName": "Vladimir","lastName": "Vladimirovich","middleName": "Putout", }    | 2021-04-15 14:49:36.234504 +00:00 
  7 | {"firstName": "Petr",    "lastName": "Petrov",       "middleName": "Petrovich", } | 2021-04-10 14:49:36.234504 +00:00 
  8 | {"firstName": "Ivan",    "lastName": "Ivanov",       "middleName": "Ivanovich", } | 2021-04-01 14:49:36.234504 +00:00 
  9 | {"firstName": "Ignat",   "lastName": "Ignatov",      "middleName": "Ignatovich", }| 2021-04-06 14:49:36.234504 +00:00 
  10| {"firstName": "Vladimir","lastName": "Vladimirovich","middleName": "Putout", }    | 2021-04-17 14:49:36.234504 +00:00 
  11| {"firstName": "Ivan",    "lastName": "Ivanov",       "middleName": "Ivanovich", } | 2021-04-12 14:49:36.234504 +00:00

p.s.There可能是“发件人”栏中的其他信息，但搜索唯一性只需要通过“firstName”、“lastName”、“middleName”

有必要 return 一个由唯一名称和最新日期组成的结果。特别是，我想得到结果：

id |                                      sender                                        | last login date                 
----+-----------------------------------------------------------------------------------+----------------------------------
  4 | {"firstName": "Nickolai","lastName": "Nickov",       "middleName": "Nikovich", }  | 2021-04-30 14:49:36.234504 +00:00 
  10| {"firstName": "Vladimir","lastName": "Vladimirovich","middleName": "Putout", }    | 2021-04-17 14:49:36.234504 +00:00 
  11| {"firstName": "Ivan",    "lastName": "Ivanov",       "middleName": "Ivanovich", } | 2021-04-12 14:49:36.234504 +00:00 
  7 | {"firstName": "Petr",    "lastName": "Petrov",       "middleName": "Petrovich", } | 2021-04-10 14:49:36.234504 +00:00 
  9 | {"firstName": "Ignat",   "lastName": "Ignatov",      "middleName": "Ignatovich", }| 2021-04-06 14:49:36.234504 +00:00

由于使用了 json，一切都变得非常复杂。我想做 - “名称”连接并执行分组和排序，但不幸的是它不起作用。

Answer 1

您可以使用 distinct on() 来执行此操作：

select distinct on (firstname, lastname) id, sender, last_login_date
from (
   select id, sender, last_login_date, 
          sender ->> 'firstName' as firstname,
          sender ->> 'lastName' as lastname
   from the_table
) t
order by firstname, lastname, last_login_date desc

Answer 2

您可以使用 window 函数来完成：

select * from 
 ( 
  select * ,rank() over (partition by sender->> 'firstName',sender->> 'lastName' order by last_login_date desc) rn
  from yourtable
 ) t
where rn = 1
order by last_login_date desc

db<>fiddle here

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