使用一个字段很容易找到重复项：
SELECT email, 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 asd@asd.com
2 Sam asd@asd.com
3 Tom asd@asd.com
4 Bob bob@asd.com
5 Tom asd@asd.com
这个查询将告诉我们John、Sam、Tom和Tom，因为他们都有相同的电子邮件。
然而，我想要的是获得相同电子邮件和名称的副本。
也就是说，我想得到“汤姆”，“汤姆”。
我需要这个的原因是：我犯了一个错误，允许插入重复的名称和电子邮件值。现在我需要删除/更改重复项，所以我需要先找到它们。
当前回答
试试看：
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
输出：
name email CountOf
---------- ----------- -----------
John John-email 2
sam sam-email 2
(2 row(s) affected)
如果您想要重复数据集的ID，请使用以下命令：
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
输出：
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
输出：
id name email
----------- ---------- --------------
1 John John-email
3 fred John-email
4 fred fred-email
5 sam sam-email
(4 row(s) affected)
其他回答
select name, email
, case
when ROW_NUMBER () over (partition by name, email order by name) > 1 then 'Yes'
else 'No'
end "duplicated ?"
from users
在使用Microsoft Access的情况下，此方法有效：
CREATE TABLE users (id int, name varchar(10), email varchar(50));
INSERT INTO users VALUES (1, 'John', 'asd@asd.com');
INSERT INTO users VALUES (2, 'Sam', 'asd@asd.com');
INSERT INTO users VALUES (3, 'Tom', 'asd@asd.com');
INSERT INTO users VALUES (4, 'Bob', 'bob@asd.com');
INSERT INTO users VALUES (5, 'Tom', 'asd@asd.com');
SELECT name, email, COUNT(*) AS CountOf
FROM users
GROUP BY name, email
HAVING COUNT(*)>1;
DELETE *
FROM users
WHERE id IN (
SELECT u1.id
FROM users u1, users u2
WHERE u1.name = u2.name AND u1.email = u2.email AND u1.id > u2.id
);
感谢Tancrede Chazallet的删除代码。
试试看：
SELECT name, email
FROM users
GROUP BY name, email
HAVING ( COUNT(*) > 1 )
如何获取表中的重复记录
SELECT COUNT(EmpCode),EmpCode FROM tbl_Employees WHERE Status=1
GROUP BY EmpCode HAVING COUNT(EmpCode) > 1
你可能想试试这个
SELECT NAME, EMAIL, COUNT(*)
FROM USERS
GROUP BY 1,2
HAVING COUNT(*) > 1
