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[英]SQL alternative for fetching latest record of each item in a table using partition
[英]SQL to fetch Latest record of each item from the table
我试图查询数据库以使用max(Created_at)
并按stockId
分组获取每只股票的最新记录,但它会带来每个项目的第一个id
及其最后一个Created_at
。
我怎样才能让它集体带来最新的记录? 请帮忙。 我的查询如下:
SELECT a.id as A_id, b.id as B_id, max(b.Created_at) AS Created_at
FROM beta b
INNER JOIN alpha a ON b.a_id = a.id
GROUP BY a.id
您可以使用诸如ROW_NUMBER()
类的分析函数:
SELECT A_id, B_id , Created_at
FROM
(
SELECT a.id as A_id, b.id as B_id , b.Created_at,
ROW_NUMBER() OVER (PARTITION BY a.id ORDER BY b.Created_at DESC) as rn
FROM beta b
JOIN alpha a ON b.a_id = a.id
) q
WHERE rn = 1
您的记录按 stockID( a.id
) 分组,并在按created_at
列降序排序后选择最新的记录。 如果关系(每个分组stockId
均等created_at
值)很重要并且所有令人满意的结果都应包含在结果集中,则将ROW_NUMBER()
替换为DENSE_RANK()
。
据我所知,你需要这样
declare @item table
(
itemid int
,itemname varchar(100)
)
insert into @item
values(1,'A'),(2,'B'),(3,'C')
declare @stock table
(
itemid int
,stockid int
,updatedate datetime
)
insert into @stock
values(1,1,'2020-08-04 13:11'),(1,1,'2020-08-04 14:11')
,(1,2,'2020-08-04 15:11'),(1,2,'2020-08-04 14:11')
select * from @item a
inner join
(select stockid,itemid,max(updatedate)lastupdatedate from @stock
group by stockid,itemid
)b on a.itemid=b.itemid
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