Sql 在时间戳单元格中选择最近的条目
我有两张桌子:Sql 在时间戳单元格中选择最近的条目,sql,postgresql,datetime,inner-join,greatest-n-per-group,Sql,Postgresql,Datetime,Inner Join,Greatest N Per Group,我有两张桌子: User: ======================= id | Name | Email ======================= 1 | User-A| a@mail 2 | User-B| b@mail ======================= Entry: ================================================= id | agree | createdOn
User:
=======================
id | Name | Email
=======================
1 | User-A| a@mail
2 | User-B| b@mail
=======================
Entry:
=================================================
id | agree | createdOn | userId
=================================================
1 | true | 2020-11-10 19:22:23 | 1
2 | false | 2020-11-10 22:22:23 | 1
3 | true | 2020-11-11 12:22:23 | 1
4 | true | 2020-11-04 22:22:23 | 2
5 | false | 2020-11-12 02:22:23 | 2
================================================
我需要得到以下结果:
=============================================================
Name | Email | agree | createdOn
=============================================================
User-A | a@mail | true | 2020-11-11 22:22:23
User-B | b@mail | false | 2020-11-12 02:22:23
=============================================================
我正在运行的Postgres查询是:
select distinct on (e."createdOn", u.id)
u.id , e.id ,u."Name" , u.email, e.agree, e."createdOn" from "user" u
inner join public.entry e on u."id" = e."userId"
order by "createdOn" desc
但问题是,它在执行连接后返回所有条目!其中我只需要
createdOn
单元格的最新条目。您需要每个用户的最新条目。为此,您需要distinct on
子句中的用户id,而不需要其他列。这保证每个用户在结果集中有一行
然后,您需要将该列放在orderby
子句的第一位,然后是createdondesc
。这将打破联系,并决定在每个组中保留哪一行:
select distinct on (u.id) u.id , e.id ,u."Name" , u.email, e.agree, e."createdOn"
from "user" u
inner join public.entry e on u."id" = e."userId"
order by u.id, "createdOn" desc
您还可以使用row_number选择最新的行,然后进行连接
SELECT * FROM USER A
LEFT JOIN (
SELECT * FROM (
SELECT *,ROW_NUMBER() OVER(PARTITION BY USERID ORDER BY CREATEDON DESC) AS RN
FROM ENTRY
) K WHERE RN = 1
) B
ON A.ID = B.USERID
尝试使用createdon=max(createdon)函数。按用户分组在(u.id)上不同
?