Mysql Query删除重复项

Question

我有类似下面的重复结果，其中某些列可能包含数据，但可能不是

| contact_info | icon | id  | title         | lastmodified_by  |
+--------------+------+-----+---------------+------------------+
|          169 |  305 | 123 | Whakarewarewa | 2011100400305262 |
|         NULL | NULL | 850 | Whakarewarewa | NULL             |
+--------------+------+-----+---------------+----------------



| contact_info | icon | id  | title         | lastmodified_by  |
+--------------+------+-----+---------------+------------------+
|         NULL | NULL | 123 | Paris         | NULL             |
|         NULL | NULL | 850 | Paris         | NULL             |
+--------------+------+-----+---------------+----------------

我想删除具有较少数据的记录，如果所有字段值完全相同，则删除任何行。 有这样的千条记录。

Answer 1

尝试这个两步解决方案：

运行此查询以查看所有重复项 - 记录数据较少 -

SELECT t1.* FROM table t1
  JOIN (
    SELECT
      title,
      MIN(IF(contact_info IS NULL, 0, 1) + IF(contact_info IS NULL, 0, 1) + IF(lastmodified_by IS NULL, 0, 1)) min_value_data,
      MAX(IF(contact_info IS NULL, 0, 1) + IF(contact_info IS NULL, 0, 1) + IF(lastmodified_by IS NULL, 0, 1)) max_value_data
    FROM table GROUP BY title HAVING min_value_data <> max_value_data
  ) t2
  ON t1.title = t2.title AND IF(t1.contact_info IS NULL, 0, 1) + IF(t1.contact_info IS NULL, 0, 1) + IF(t1.lastmodified_by IS NULL, 0, 1) <> t2.max_value_data

将其重写为DELETE语句并执行。

---

然后运行此查询以删除除min ID之外的所有重复项：

DELETE t1 FROM table t1
  JOIN (SELECT MIN(id) id, title FROM table GROUP BY title) t2
    ON t1.id <> t2.id AND t1.title = t2.title;

Answer 2

使用此选项重复，可以随意将其更改为删除语句：

SELECT * FROM `test`,
(SELECT title, count( title ) AS ttl
FROM `test`
GROUP BY title
HAVING ttl >1) AS sub

WHERE test.title = sub.title
AND contact_info IS NULL AND lastmodified_by IS NULL 

Answer 3

主表= tes1

创建临时

  

CREATE TEMPORARY TABLE my_temp（id INT（20）NOT NULL）ENGINE = MEMORY;

     

填写id以删除

     

INSERT INTO my_temp（id）SELECT id FROM tes1 AS main，（SELECT title，count（title）AS ttl FROM tes1 GROUP BY   标题HETING ttl＆gt; 1）AS sub WHERE main.title = sub.title AND   main.contact_info IS NULL AND main.lastmodified_by IS NULL GROUP BY   main.contact_info，main.icon，main.title，main.lastmodified_by;

     

删除！

     

DELETE FROM tes1 WHERE id IN（从my_temp中选择id）;

     

清理，注意：我们真的需要这个吗？

     

DROP TABLE my_temp;