我有这个查询片段的SQLServer，但我认为它可以用在其他DBMS与小的变化:

DELETE
FROM Table
WHERE Table.idTable IN  (  
    SELECT MAX(idTable)
    FROM idTable
    GROUP BY field1, field2, field3
    HAVING COUNT(*) > 1)

我忘了告诉您，这个查询不会删除重复行中id最低的行。如果这对你有用，试试这个查询:

DELETE
FROM jobs
WHERE jobs.id IN  (  
    SELECT MAX(id)
    FROM jobs
    GROUP BY site_id, company, title, location
    HAVING COUNT(*) > 1)

我有这个查询片段的SQLServer，但我认为它可以用在其他DBMS与小的变化:

DELETE
FROM Table
WHERE Table.idTable IN  (  
    SELECT MAX(idTable)
    FROM idTable
    GROUP BY field1, field2, field3
    HAVING COUNT(*) > 1)

我忘了告诉您，这个查询不会删除重复行中id最低的行。如果这对你有用，试试这个查询:

DELETE
FROM jobs
WHERE jobs.id IN  (  
    SELECT MAX(id)
    FROM jobs
    GROUP BY site_id, company, title, location
    HAVING COUNT(*) > 1)

为了复制具有唯一列的记录，例如COL1,COL2, COL3不应该被复制(假设我们在表结构中遗漏了3个唯一列，并且在表中添加了多个重复项)

DROP TABLE TABLE_NAME_copy;
CREATE TABLE TABLE_NAME_copy LIKE TABLE_NAME;
INSERT INTO TABLE_NAME_copy
SELECT * FROM TABLE_NAME
GROUP BY COLUMN1, COLUMN2, COLUMN3; 
DROP TABLE TABLE_NAME;
ALTER TABLE TABLE_NAME_copy RENAME TO TABLE_NAME;

希望将有助于开发。

如果不想更改列属性，那么可以使用下面的查询。

因为你有一个列，它有唯一的id(例如，auto_increment列)，你可以用它来删除重复项:

DELETE `a`
FROM
    `jobs` AS `a`,
    `jobs` AS `b`
WHERE
    -- IMPORTANT: Ensures one version remains
    -- Change "ID" to your unique column's name
    `a`.`ID` < `b`.`ID`

    -- Any duplicates you want to check for
    AND (`a`.`title` = `b`.`title` OR `a`.`title` IS NULL AND `b`.`title` IS NULL)
    AND (`a`.`company` = `b`.`company` OR `a`.`company` IS NULL AND `b`.`company` IS NULL)
    AND (`a`.`site_id` = `b`.`site_id` OR `a`.`site_id` IS NULL AND `b`.`site_id` IS NULL);

在MySQL中，你可以用空安全的相等操作符(又名“宇宙飞船操作符”)来简化它:

DELETE `a`
FROM
    `jobs` AS `a`,
    `jobs` AS `b`
WHERE
    -- IMPORTANT: Ensures one version remains
    -- Change "ID" to your unique column's name
    `a`.`ID` < `b`.`ID`

    -- Any duplicates you want to check for
    AND `a`.`title` <=> `b`.`title`
    AND `a`.`company` <=> `b`.`company`
    AND `a`.`site_id` <=> `b`.`site_id`;

删除表中重复的记录。

delete from job s 
where rowid < any 
(select rowid from job k 
where s.site_id = k.site_id and 
s.title = k.title and 
s.company = k.company);

or

delete from job s 
where rowid not in 
(select max(rowid) from job k 
where s.site_id = k.site_id and
s.title = k.title and 
s.company = k.company);

从8.0版(2018)开始，MySQL终于支持窗口函数了。

窗口函数既方便又高效。下面是一个演示如何使用它们来解决这个任务的解决方案。

在子查询中，可以使用ROW_NUMBER()为表中columnn1 /column2组中的每条记录分配位置，按id排序。如果没有重复项，记录将获得第1行。如果存在副本，它们将按升序编号(从1开始)。

一旦子查询中的记录正确编号，外层查询只删除行号不是1的所有记录。

查询:

DELETE FROM tablename
WHERE id IN (
    SELECT id
    FROM (
        SELECT 
            id, 
            ROW_NUMBER() OVER(PARTITION BY column1, column2 ORDER BY id) rn
        FROM output
    ) t
    WHERE rn > 1
)