Sql 删除重复的行并更新引用

如何删除一个表中的重复行，并将另一个表中的引用更新到剩余行？重复只发生在名称中。Id列是标识列

例子： 假设我们有两个表double和Data

现在我在Doubls表中有两个条目：

Id Name
1  Foo
2  Foo

和数据表中的两个条目：

ID DoublesId
1  1
2  2

Id DoublesId
1  1
2  1 

最后，Double表中应只有一个条目：

Id Name
1  Foo

和数据表中的两个条目：

ID DoublesId
1  1
2  2

Id DoublesId
1  1
2  1 

---

在doubles表中，每个名称可以有任意数量的重复行，最多30行，也可以是常规的“单”行。

注意：我已冒昧地将您的Id分别重命名为DoubleID和DataID。我觉得这更容易相处

DECLARE @Doubles TABLE (DoubleID INT, Name VARCHAR(50))
DECLARE @Data TABLE (DataID INT, DoubleID INT)

INSERT INTO @Doubles VALUES (1, 'Foo')
INSERT INTO @Doubles VALUES (2, 'Foo')
INSERT INTO @Doubles VALUES (3, 'Bar')
INSERT INTO @Doubles VALUES (4, 'Bar')

INSERT INTO @Data VALUES (1, 1)
INSERT INTO @Data VALUES (1, 2)
INSERT INTO @Data VALUES (1, 3)
INSERT INTO @Data VALUES (1, 4)

SELECT * FROM @Doubles
SELECT * FROM @Data

UPDATE @Data
SET DoubleID = MinDoubleID
FROM    @Data dt
        INNER JOIN @Doubles db ON db.DoubleID = dt.DoubleID
        INNER JOIN (
            SELECT    db.Name, MinDoubleID = MIN(db.DoubleID)
            FROM      @Doubles db
            GROUP BY  db.Name
        ) dbmin ON dbmin.Name = db.Name

/* Kudos to quassnoi */
;WITH q AS (
    SELECT Name, ROW_NUMBER() OVER (PARTITION BY Name ORDER BY Name) AS rn
    FROM @Doubles
    )
DELETE  
FROM    q
WHERE   rn > 1

SELECT * FROM @Doubles
SELECT * FROM @Data

---

看看这个，我试过了，效果很好

--create table Doubles  (   Id int,   Name varchar(50))

--create table Data(    Id int,    DoublesId int)

--select * from doubles
--select * from data

Declare @NonDuplicateID int
Declare @NonDuplicateName varchar(max)
DECLARE @sqlQuery nvarchar(max)
DECLARE DeleteDuplicate CURSOR FOR

SELECT Max(id),name AS SingleID FROM Doubles
GROUP BY [NAME]

OPEN DeleteDuplicate 
FETCH NEXT FROM DeleteDuplicate INTO @NonDuplicateID, @NonDuplicateName
--Fetch next record
WHILE @@FETCH_STATUS = 0
BEGIN

--select b.ID , b.DoublesID, a.[name],a.id asdasd
--from doubles a    inner join  data b
--on
--a.ID=b.DoublesID
--where b.DoublesID<>@NonDuplicateID
--and a.[name]=@NonDuplicateName

print '---------------------------------------------';

select 
@sqlQuery = 
      'update b
        set b.DoublesID=' + cast(@NonDuplicateID as varchar(50)) + '
        from 
        doubles a
            inner join
        data b
            on
        a.ID=b.DoublesID
        where b.DoublesID<>' +  cast(@NonDuplicateID as varchar(50)) +
        ' and a.[name]=''' +  cast(@NonDuplicateName as varchar(max)) +'''';

print @sqlQuery
exec sp_executeSQL @sqlQuery
print '---------------------------------------------';

-- now move the cursor
FETCH NEXT FROM DeleteDuplicate INTO @NonDuplicateID ,@NonDuplicateName
END

CLOSE DeleteDuplicate --Close cursor
DEALLOCATE DeleteDuplicate --Deallocate cursor

---- Delete duplicate rows from original table
DELETE
FROM doubles
WHERE ID NOT IN
(
    SELECT MAX(ID)
    FROM doubles
    GROUP BY [NAME]
)

如果这对你有帮助，请告诉我

谢谢

---

~Aamod

我还没有运行这个，但希望它应该是正确的，并且离最终解决方案足够近，可以让您到达那里。如果你愿意，请告诉我任何错误，我会更新答案

--updates the data table to the min ids for each name
update Data
set id = final_id
from
  Data
join
  Doubles 
on Doubles.id = Data.id
join
(
  select 
    name
    min(id) as final_id
  from Doubles
  group by name
) min_ids
on min_ids.name = Doubles.name

--deletes redundant ids from the Doubles table
delete 
from Doubles
where id not in
(
  select 
    min(id) as final_id
  from Doubles
  group by name
)

---

如果你使用的是MYSQL，下面的内容对我很有用。我做了两步

步骤1->将所有数据行更新为一个id最低的双表引用 步骤2->删除保留最低id的所有重复项 步骤1->

update Data 
join
  Doubles 
on Data.DoublesId = Doubles.id
join
(
  select name, min(id) as final_id
  from Doubles
  group by name
) min_ids
on min_ids.name = Doubles.name
set DoublesId = min_ids.final_id;

第2步->

DELETE c1 FROM Doubles c1
INNER JOIN Doubles c2 
WHERE
    c1.id > c2.id AND 
    c1.name = c2.name;

---

我自己也不明白，但这个示例代码似乎在SQLServer2008上工作。