在SQL表中查找重复值

Question

用一个字段很容易找到duplicates：

SELECT name, COUNT(email) 
FROM users
GROUP BY email
HAVING COUNT(email) > 1

所以，如果我们有一张桌子

ID   NAME   EMAIL
1    John   [email protected]
2    Sam    [email protected]
3    Tom    [email protected]
4    Bob    [email protected]
5    Tom    [email protected]

这个查询将给我们John，Sam，Tom，Tom，因为他们都有相同的email。

但是，我想要的是使用相同的email和name获得重复。

也就是说，我想得到“汤姆”，“汤姆”。

我需要这个的原因：我犯了一个错误，并允许插入重复的name和email值。现在我需要删除/更改重复项，所以我需要先找到它们。

Answer 1

SELECT
    name, email, COUNT(*)
FROM
    users
GROUP BY
    name, email
HAVING 
    COUNT(*) > 1

只需在两个列上分组。

注意：较旧的ANSI标准是在GROUP BY中包含所有非聚合列，但这已经改变了"functional dependency"的想法：

在关系数据库理论中，函数依赖性是来自数据库的关系中的两组属性之间的约束。换句话说，函数依赖是描述关系中属性之间关系的约束。

支持不一致：

最近的PostgreSQL supports it。
SQL Server（与SQL Server 2017一样）仍然需要GROUP BY中的所有非聚合列。
MySQL是不可预测的，你需要sql_mode=only_full_group_by： GROUP BY lname ORDER BY showing wrong results; Which is the least expensive aggregate function in the absence of ANY()（见接受答复中的评论）。
Oracle不够主流（警告：幽默，我不了解Oracle）。

Answer 2

这将选择/删除除每组重复项中的一条记录之外的所有重复记录。因此，删除会留下所有唯一记录+来自每组重复项的一条记录。

选择重复：

SELECT *
FROM table
WHERE
    id NOT IN (
        SELECT MIN(id)
        FROM table
        GROUP BY column1, column2
);

删除重复项：

DELETE FROM table
WHERE
    id NOT IN (
        SELECT MIN(id)
        FROM table
        GROUP BY column1, column2
);

注意大量记录，可能会导致性能问题。

Answer 3

select id,name,COUNT(*) from India group by Id,Name having COUNT(*)>1

Answer 4

如果你想看看你的表中是否有任何重复的行，我使用下面的Query：

create table my_table(id int, name varchar(100), email varchar(100));

insert into my_table values (1, 'shekh', '[email protected]');
insert into my_table values (1, 'shekh', '[email protected]');
insert into my_table values (2, 'Aman', '[email protected]');
insert into my_table values (3, 'Tom', '[email protected]');
insert into my_table values (4, 'Raj', '[email protected]');


Select COUNT(1) As Total_Rows from my_table 
Select Count(1) As Distinct_Rows from ( Select Distinct * from my_table) abc

Answer 5

我们如何计算重复的值？要么重复2次，要么重复2次。只计算它们，而不是按组计算。

就像

select COUNT(distinct col_01) from Table_01

Answer 6

这是我想出的容易的事情。它使用公用表表达式（CTE）和分区窗口（我认为这些功能在SQL 2008及更高版本中）。

此示例查找名称和dob重复的所有学生。要检查重复的字段是否在OVER子句中。您可以在投影中包含所需的任何其他字段。

with cte (StudentId, Fname, LName, DOB, RowCnt)
as (
SELECT StudentId, FirstName, LastName, DateOfBirth as DOB, SUM(1) OVER (Partition By FirstName, LastName, DateOfBirth) as RowCnt
FROM tblStudent
)
SELECT * from CTE where RowCnt > 1
ORDER BY DOB, LName

Answer 7

通过使用CTE，我们也可以找到这样的重复值

with MyCTE
as
(
select Name,EmailId,ROW_NUMBER() over(PARTITION BY EmailId order by id) as Duplicate from [Employees]

)
select * from MyCTE where Duplicate>1

Answer 8

 select emp.ename, emp.empno, dept.loc 
          from emp
 inner join dept 
          on dept.deptno=emp.deptno
 inner join
    (select ename, count(*) from
    emp
    group by ename, deptno
    having count(*) > 1)
 t on emp.ename=t.ename order by emp.ename
/

Answer 9

SELECT id, COUNT(id) FROM table1 GROUP BY id HAVING COUNT(id)>1;

我认为这可以正常搜索特定列中的重复值。

Answer 10

select name, email
, case 
when ROW_NUMBER () over (partition by name, email order by name) > 1 then 'Yes'
else 'No'
end "duplicated ?"
from users

Answer 11

这也应该有用，也许试一试。

  Select * from Users a
            where EXISTS (Select * from Users b 
                where (     a.name = b.name 
                        OR  a.email = b.email)
                     and a.ID != b.id)

特别适用于您的情况如果您搜索具有某种前缀或一般更改的重复项，例如邮件中的新域名。那么你可以在这些列上使用replace（）

Answer 12

试试这个：

declare @YourTable table (id int, name varchar(10), email varchar(50))

INSERT @YourTable VALUES (1,'John','John-email')
INSERT @YourTable VALUES (2,'John','John-email')
INSERT @YourTable VALUES (3,'fred','John-email')
INSERT @YourTable VALUES (4,'fred','fred-email')
INSERT @YourTable VALUES (5,'sam','sam-email')
INSERT @YourTable VALUES (6,'sam','sam-email')

SELECT
    name,email, COUNT(*) AS CountOf
    FROM @YourTable
    GROUP BY name,email
    HAVING COUNT(*)>1

OUTPUT：

name       email       CountOf
---------- ----------- -----------
John       John-email  2
sam        sam-email   2

(2 row(s) affected)

如果你想要复制的ID使用这个：

SELECT
    y.id,y.name,y.email
    FROM @YourTable y
        INNER JOIN (SELECT
                        name,email, COUNT(*) AS CountOf
                        FROM @YourTable
                        GROUP BY name,email
                        HAVING COUNT(*)>1
                    ) dt ON y.name=dt.name AND y.email=dt.email

OUTPUT：

id          name       email
----------- ---------- ------------
1           John       John-email
2           John       John-email
5           sam        sam-email
6           sam        sam-email

(4 row(s) affected)

要删除重复项，请尝试：

DELETE d
    FROM @YourTable d
        INNER JOIN (SELECT
                        y.id,y.name,y.email,ROW_NUMBER() OVER(PARTITION BY y.name,y.email ORDER BY y.name,y.email,y.id) AS RowRank
                        FROM @YourTable y
                            INNER JOIN (SELECT
                                            name,email, COUNT(*) AS CountOf
                                            FROM @YourTable
                                            GROUP BY name,email
                                            HAVING COUNT(*)>1
                                        ) dt ON y.name=dt.name AND y.email=dt.email
                   ) dt2 ON d.id=dt2.id
        WHERE dt2.RowRank!=1
SELECT * FROM @YourTable

OUTPUT：

id          name       email
----------- ---------- --------------
1           John       John-email
3           fred       John-email
4           fred       fred-email
5           sam        sam-email

(4 row(s) affected)

Answer 13

如果要查找重复数据（通过一个或多个标准）并选择实际行。

with MYCTE as (
    SELECT DuplicateKey1
        ,DuplicateKey2 --optional
        ,count(*) X
    FROM MyTable
    group by DuplicateKey1, DuplicateKey2
    having count(*) > 1
) 
SELECT E.*
FROM MyTable E
JOIN MYCTE cte
ON E.DuplicateKey1=cte.DuplicateKey1
    AND E.DuplicateKey2=cte.DuplicateKey2
ORDER BY E.DuplicateKey1, E.DuplicateKey2, CreatedAt

http://developer.azurewebsites.net/2014/09/better-sql-group-by-find-duplicate-data/

Answer 14

SELECT * FROM users u where rowid = (select max(rowid) from users u1 where
u.email=u1.email);

Answer 15

SELECT column_name,COUNT(*) FROM TABLE_NAME GROUP BY column1, HAVING COUNT(*) > 1;

Answer 16

删除名称重复的记录

;WITH CTE AS    
(

    SELECT ROW_NUMBER() OVER (PARTITION BY name ORDER BY name) AS T FROM     @YourTable    
)

DELETE FROM CTE WHERE T > 1

Answer 17

检查表中的重复记录。

select * from users s 
where rowid < any 
(select rowid from users k where s.name = k.name and s.email = k.email);

要么

select * from users s 
where rowid not in 
(select max(rowid) from users k where s.name = k.name and s.email = k.email);

删除表中的重复记录。

delete from users s 
where rowid < any 
(select rowid from users k where s.name = k.name and s.email = k.email);

要么

delete from users s 
where rowid not in 
(select max(rowid) from users k where s.name = k.name and s.email = k.email);

Answer 18

我们可以使用这里有关于聚合函数的工作，如下所示

create table #TableB (id_account int, data int, [date] date)
insert into #TableB values (1 ,-50, '10/20/2018'),
(1, 20, '10/09/2018'),
(2 ,-900, '10/01/2018'),
(1 ,20, '09/25/2018'),
(1 ,-100, '08/01/2018')  

SELECT id_account , data, COUNT(*)
FROM #TableB
GROUP BY id_account , data
HAVING COUNT(id_account) > 1

drop table #TableB

这里有两个字段id_account和数据与Count（*）一起使用。因此，它将提供在两列中具有多于一倍相同值的所有记录。

我们有些错误地错过了在SQL服务器表中添加任何约束并且在前端应用程序的所有列中插入了重复的记录。然后我们可以使用下面的查询从表中删除重复的查询。

SELECT DISTINCT * INTO #TemNewTable FROM #OriginalTable
TRUNCATE TABLE #OriginalTable
INSERT INTO #OriginalTable SELECT * FROM #TemNewTable
DROP TABLE #TemNewTable

在这里，我们获取了原始表的所有不同记录，并删除了原始表的记录。我们再次将新表中的所有不同值插入到原始表中，然后删除新表。

Answer 19

您可以使用SELECT DISTINCT关键字来删除重复项。您还可以按名称进行过滤，并在表格中获取具有该名称的所有人。

Answer 20

你可能想试试这个

SELECT NAME, EMAIL, COUNT(*)
FROM USERS
GROUP BY 1,2
HAVING COUNT(*) > 1

Answer 21

如何在表中获取重复记录

 SELECT COUNT(EmpCode),EmpCode FROM tbl_Employees WHERE Status=1 
 GROUP BY EmpCode HAVING COUNT(EmpCode) > 1

Answer 22

试试这个：

SELECT name, email
FROM users
GROUP BY name, email
HAVING ( COUNT(*) > 1 )

Answer 23

如果你想删除重复项，这里有一个更简单的方法，而不是在三重子选择中找到偶数/奇数行：

SELECT id, name, email 
FROM users u, users u2
WHERE u.name = u2.name AND u.email = u2.email AND u.id > u2.id

所以要删除：

DELETE FROM users
WHERE id IN (
    SELECT id/*, name, email*/
    FROM users u, users u2
    WHERE u.name = u2.name AND u.email = u2.email AND u.id > u2.id
)

更容易阅读和理解恕我直言

注意：唯一的问题是您必须执行请求，直到没有删除任何行，因为每次只删除每个副本中的一个

Answer 24

请尝试以下方法：

SELECT * FROM
(
    SELECT Id, Name, Age, Comments, Row_Number() OVER(PARTITION BY Name, Age ORDER By Name)
        AS Rank 
        FROM Customers
) AS B WHERE Rank>1

Answer 25

 SELECT name, email 
    FROM users
    WHERE email in
    (SELECT email FROM users
    GROUP BY email 
    HAVING COUNT(*)>1)

Answer 26

派对有点晚了，但我找到了一个很酷的解决方法来找到所有重复的ID：

SELECT GROUP_CONCAT( id )
FROM users
GROUP BY email
HAVING ( COUNT(email) > 1 )

Answer 27

试试这段代码

WITH CTE AS

( SELECT Id, Name, Age, Comments, RN = ROW_NUMBER()OVER(PARTITION BY Name,Age ORDER BY ccn)
FROM ccnmaster )
select * from CTE

Answer 28

如果您使用Oracle，这种方式更可取：

create table my_users(id number, name varchar2(100), email varchar2(100));

insert into my_users values (1, 'John', '[email protected]');
insert into my_users values (2, 'Sam', '[email protected]');
insert into my_users values (3, 'Tom', '[email protected]');
insert into my_users values (4, 'Bob', '[email protected]');
insert into my_users values (5, 'Tom', '[email protected]');

commit;

select *
  from my_users
 where rowid not in (select min(rowid) from my_users group by name, email);

在SQL表中查找重复值

问题描述投票：1659回答：28

28个回答

最新问题

在SQL表中查找重复值

问题描述 投票：1659回答：28

28个回答

最新问题

问题描述投票：1659回答：28