[英]Find record closest to a given date for each group - SQL
我是sql新手。 假設我們有一個這樣的表:
+-------+----------+-----------+
|userid | statusid | date |
+-------+----------+-----------+
| 1 | 1 | 2018-10-10|
| 1 | 2 | 2018-10-12|
| 2 | 1 | 2018-09-25|
| 2 | 1 | 2018-10-01|
+-------+----------+-----------+
我需要獲取每個用戶ID的stateid,使其日期盡可能接近給定的日期。 說我的給定日期是2018-10-01。 我該怎么做? 我嘗試了各種groupby和partition by,但是沒有任何效果。 有人可以幫忙嗎?
編輯:我的數據庫是亞馬遜redshift
您可以使用row_number()
窗口分析函數,按日期差的絕對值排序。
(請注意, row_number()
在MySQL 8-
不起作用,因此未使用該函數,但使用了abs()
函數。)
我不知道您的DBMS
該解決方案適用於Oracle
:
with tab(userid, statusid, "date") as
(
select 1,1,date'2018-10-10' from dual union all
select 1,2,date'2018-10-12' from dual union all
select 2,1,date'2018-09-25' from dual union all
select 2,1,date'2018-10-02' from dual
)
select tt.userid, tt.statusid, tt."date"
from
(
select t.userid, t.statusid , t."date",
row_number() over (partition by t.userid
order by abs("date" - date'2018-10-01')) as rn
from tab t
) tt
where tt.rn = 1
此解決方案適用於SQL Server
:
with tab([userid], [statusid], [date]) as
(
select 1,1,'2018-10-10' union all
select 1,2,'2018-10-12' union all
select 2,1,'2018-09-25' union all
select 2,1,'2018-10-02'
)
select tt.[userid], tt.[statusid], tt.[date]
from
(
select t.[userid], t.[statusid] , t.[date],
row_number() over (partition by t.[userid]
order by abs(datediff(day,[date],'2018-10-01'))) as rn
from tab t
) tt
where tt.rn = 1
該解決方案適用於My SQL
:
select tt.userid, tt.statusid, tt.date
from
(
select t.userid, t.statusid , t.date,
@rn := if(@iter = t.userid, @rn + 1, 1) as rn,
@iter := t.userid,
abs(date - date'2018-10-01') as df
from tab t
join (select @iter := 0, @rn := 0) as q_iter
order by t.userid, abs(date - date'2018-10-01')
) tt
where tt.rn = 1
此解決方案適用於PostGRES
:
with tab(userid, statusid, date) as
(
select 1,1,'2018-10-10' union all
select 1,2,'2018-10-12' union all
select 2,1,'2018-09-25' union all
select 2,1,'2018-10-02'
)
select tt.userid, tt.statusid, tt.date
from
(
select t.userid, t.statusid , t.date,
row_number() over (partition by t.userid
order by abs(date::date-'2018-10-01'::date)) as rn
from tab t
) tt
where tt.rn = 1
通常對於這種類型的問題,您希望日期在給定日期或之前。
如果是這樣的話:
select t.*
from t
where t.date = (select max(t2.date)
from t t2
where t2.userid = t.userid and t2.date <= '2018-10-01'
);
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