下面是我用过的方法，它很有效:

create table temp_table like my_table;

T_id是唯一的列

insert into temp_table (id) select id from my_table GROUP by t_id;
delete from my_table where id not in (select id from temp_table);
drop table temp_table;

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`;

更快的方法是在临时表中插入不同的行。使用delete，我花了几个小时从一个800万行的表中删除重复项。使用insert和distinct，只花了13分钟。

CREATE TABLE tempTableName LIKE tableName;  
CREATE INDEX ix_all_id ON tableName(cellId,attributeId,entityRowId,value);  
INSERT INTO tempTableName(cellId,attributeId,entityRowId,value) SELECT DISTINCT cellId,attributeId,entityRowId,value FROM tableName;  
TRUNCATE TABLE tableName;
INSERT INTO tableName SELECT * FROM tempTableName; 
DROP TABLE tempTableName;  

这个解决方案将把重复的数据移到一个表中，唯一的数据移到另一个表中。

-- speed up creating uniques table if dealing with many rows
CREATE INDEX temp_idx ON jobs(site_id, company, title, location);

-- create the table with unique rows
INSERT jobs_uniques SELECT * FROM
    (
    SELECT * 
    FROM jobs
    GROUP BY site_id, company, title, location
    HAVING count(1) > 1
    UNION
    SELECT *
    FROM jobs
    GROUP BY site_id, company, title, location
    HAVING count(1) = 1
) x

-- create the table with duplicate rows
INSERT jobs_dupes 
SELECT * 
FROM jobs
WHERE id NOT IN
(SELECT id FROM jobs_uniques)

-- confirm the difference between uniques and dupes tables
SELECT COUNT(1)
AS jobs, 
(SELECT COUNT(1) FROM jobs_dupes) + (SELECT COUNT(1) FROM jobs_uniques)
AS sum
FROM jobs

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。

简单和快速的所有情况:

CREATE TEMPORARY TABLE IF NOT EXISTS _temp_duplicates AS (SELECT dub.id FROM table_with_duplications dub GROUP BY dub.field_must_be_uniq_1, dub.field_must_be_uniq_2 HAVING COUNT(*)  > 1);

DELETE FROM table_with_duplications WHERE id IN (SELECT id FROM _temp_duplicates);