MySQL 删除表中重复记录且只保留一条

表记录

mysql> select * from score_info;
+----+------+----------+-------+
| id | name | class_no | score |
+----+------+----------+-------+
|  1 | 张三 | 高三1班  |   100 |
|  2 | 张三 | 高三1班  |   100 |
|  3 | 张三 | 高三1班  |    98 |
|  4 | 李四 | 高三2班  |    88 |
|  5 | 王五 | 高三3班  |    90 |
|  6 | 王五 | 高三3班  |    92 |
+----+------+----------+-------+

SQL 语句

-- 删除 name 一样的重复记录
DELETE FROM score_info
WHERE id NOT IN (
  SELECT t.id
  FROM (
    SELECT id
    FROM score_info si
    WHERE (
      SELECT COUNT(1)
      FROM score_info t
      WHERE `name` = si.`name` AND id > si.id
    ) < 1
  ) t
);

-- 删除 name 一样的重复记录
DELETE FROM score_info
WHERE id IN (
  SELECT t.id
  FROM (
    SELECT id
    FROM score_info si
    WHERE (
      SELECT COUNT(1)
      FROM score_info
      WHERE `name` = si.`name` AND id > si.id
    ) > 0
  )t
);


-- 删除除了 id 之外其他字段完全一样的重复记录
DELETE FROM score_info
WHERE id NOT IN (
  SELECT t.id
  FROM (
    SELECT id
    FROM score_info si
    WHERE (
      SELECT COUNT(1)
      FROM score_info
      WHERE `name` = si.`name` AND class_no = si.class_no AND
              score = si.score AND id > si.id
    ) < 1
  ) t
);

-- 删除除了 id 之外其他字段完全一样的重复记录
DELETE FROM score_info
WHERE id IN (
  SELECT t.id
  FROM (
    SELECT id
    FROM score_info si
    WHERE (
      SELECT COUNT(1)
      FROM score_info
      WHERE `name` = si.`name` AND class_no = si.class_no AND
              score = si.score AND id > si.id
    ) > 0
  ) t
);


# 从数据表s1表中把姓名相同且id大于s2表中的id的记录全部删除
delete s1
from score_info s1, score_info s2
where s1.name = s2.name and s1.id > s2.id

表结构

CREATE TABLE `score_info` (
  `id` bigint(18) NOT NULL AUTO_INCREMENT,
  `name` varchar(20) DEFAULT NULL,
  `class_no` varchar(10) DEFAULT NULL,
  `score` int(5) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;