更新列 "Count" 以具有其最高重复行 ID 的值，根据 "Url" 列删除重复行

Question

// 更新列“Count”以具有其最高重复行 ID 的值，删除//基于“Url”列的重复行（仅保留具有最低 ID 的行），

| ID | First_Name | Count | Url |
| -- | ---------- | ----- | ---------- |
| 1  | A          | 10    |  www.A.com |
| 2  | B          | 21    |  www.B.com |
| 3  | C          | 12    |  www.C.com |
| 4  | D          | 31    |  www.D.com |
| 5  | A          | 13    |  www.A.com |
| 6  | D          | 18    |  www.D.com |
| 7  | A          | 5     |  www.A.com |

EXPECTED RESULT

| ID | First_Name | Count | Url |
| -- | ---------- | ----- | --------- |
| 1  | A          | 5     | www.A.com |
| 2  | B          | 21    | www.B.com |
| 3  | C          | 12    | www.C.com |
| 4  | D          | 18    | www.D.com |

Answer 1

由于你没有说明这是什么类型的数据库，我只好瞎猜了。但这是 select SQL Server Management Studio v17.9.1 中的最新副本的方法 Fiddle: https://dbfiddle.uk/?rdbms=sqlserver_2019&fiddle=e266cfbca912dc1a541f5f474a0b018d

这就是您可以 select 最新值的方法，使用此逻辑，您可以简单地更新 First_Name 匹配的值，并删除其余值等。

CREATE TABLE #testValues (
   ID int NOT NULL
   ,[First_Name] varchar(255) NOT NULL
   ,[Count]  int NULL
   ,[Url]  varchar(255) NOT NULL
   ) 

INSERT INTO #testvalues (
   ID
   ,[First_Name]
   ,[Count]
   ,[Url]
   )

VALUES (1,'A',10,'www.A.com'),
(2,'B',21,'www.B.com'),
(3,'C',12,'www.C.com'),
(4,'D',31,'www.D.com'),
(5,'A',13,'www.A.com'),
(6,'D',18,'www.D.com'),
(7,'A',5,'www.A.com');

select min(a.id) as 'ID', a.First_Name
into #lowestId
from #testValues a
group by a.first_name

SELECT a.*
into #newValues
from #testValues a
left join #testValues b
on a.First_Name=b.First_Name and a.Url=b.Url and a.id < b.ID
where b.ID is null
order by a.First_Name

select case when b.ID is null then a.ID else b.ID end as 'ID', 
a.count, 
a.first_name, 
a.url
from #newValues a
left join #lowestId b
on a.first_name=b.first_name and b.ID < a.ID
order by case when b.ID is null then a.ID else b.ID end

drop table #lowestId
drop table #newValues
drop table #testValues

Answer 2

我想你想删除按 url 分组的双精度值，所以你可以试试这个：

DELETE t FROM your_table t 
INNER JOIN (
   SELECT Url,MIN(count) AS min_count
   FROM your_table
   GROUP BY Url 
   HAVING COUNT(ID) > 1
) as t2 on t2.Url = t.Url
WHERE t.count > t2.min_count

Answer 3

不改变table结构的另一个：

UPDATE your_table yt SET yt.count = (SELECT max(yt2.id) FROM your_table yt2 WHERE yt2.Url = yt.Url AND yt.id != yt2.id);

DELETE FROM your_table yt WHERE yt.Url IN (SELECT yt2.Url from your_table WHERE yt2.id < yt.id)

更新列 "Count" 以具有其最高重复行 ID 的值，根据 "Url" 列删除重复行

update column "Count" to have the value of its highest duplicate row ID, delete duplicate rows based on the "Url" column

sql

database

sql-update