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+--------------------------------------+---------+---------------------+
解决方法
思路是这样的:首先应该按照conf_id和时间点来判断,进行分组(group by)查询,每组中再取一个就可以。分组是很简单,但是分组怎么取一个呢?我采用了中间表的形式。
创建中间表,并把数据导入中间表
复制代码 代码如下:
create table perf_linux_t like perf_linux;
insert into perf_linux_t select * from perf_linux;
复制代码 代码如下:
ALTER TABLE `perf_linux_t`
ADD COLUMN `auto_id` INT NOT NULL AUTO_INCREMENT ,
DROP PRIMARY KEY,
ADD PRIMARY KEY (`auto_id`);
先查询一下
复制代码 代码如下:
select min(auto_id) as auto_id from perf_linux_t group by insert_time ;
复制代码 代码如下:
delete from perf_linux_t where auto_id not in (select min(auto_id) as auto_id from perf_linux_t group by insert_time);
You can't specify target table 'perf_linux_t' for update in FROM clause
不能删除啊,那只能再建一个中间表了。
再建中间表
复制代码 代码如下:
create table tmp like perf_linux_t;
复制代码 代码如下:
insert into tmp select * from perf_linux_t where auto_id in (select min(auto_id) as auto_id from perf_linux_t group by insert_time,conf_id );
复制代码 代码如下:
ALTER TABLE `tmp`
DROP COLUMN `auto_id`,
DROP PRIMARY KEY;
删除原来的数据
复制代码 代码如下:
truncate table perf_linux;
复制代码 代码如下:
insert into perf_linux select * from tmp;
复制代码 代码如下:
drop table tmp;
drop table perf_linux_t;
通过这个方法,数据变为了42387条,删除了冗余的数据。但实际上程序的问题并没有完全定位,还需要观察才能定位问题。
希望本文所述对大家的mysql数据库程序设计有所帮助。