mysql触发器实时检测一条语句进行备份删除思路详解
问题描述:用户有一个这样一个需求,在一张表里会不时出现 “违规” 字样的字段,需要在出现这个字段的时候,把整行的数据删掉。这是个采集任务,如果发现有“违规”字样的数据,会整点或者什么时间进行统一上报,也无法对源头进行控制让这种数据不生成。
现在需要实现以下需求:
1.实时检测这条数据的产生,发现后删除
2.在删除之前作备份这条数据
解决思路:
需要明确解决思路,
1.首先是如何实时探测删除?询问开发,这条数据的生成方式为insert,就可以做一个当表做插入的时候,然后做一个after insert 做delete数据的触发器
2.如何进行备份?何种方式备份?能不能备份到一个表里,这个表里记录每次插入的时间,建立这个备份表可以取与原表结构基本相同,但是备份表要删除原表的自增属性,主键,外键等属性,新增一个时间戳字段,方便记录每次备份数据的时间,删除以上属性是为了能够把数据写入备份表中
3.如何在删除之前做备份呢?一开始想的是放到一个触发器就行,先把数据进行备份,然后后面跟着一条删除,测试的时候行不通
测试方案:
先准备一些测试数据和测试表
1.建立测试数据
mysql> show create table student; +---------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | table | create table | +---------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | student | create table `student` ( `sno` char(9) not null, `sname` char(20) not null, `ssex` char(2) default null, `sage` smallint default null, `sdept` char(20) default null, primary key (`sno`) ) engine=innodb default charset=utf8mb4 collate=utf8mb4_0900_ai_ci | +---------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 1 row in set (0.01 sec)
2.建立备份表。查看建表语句,正式环境是不知道原表的表结构的,需要有改原表结构,并创建新备份表的操作的
原表建表语句
mysql> show create table student; +---------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | table | create table | +---------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | student | create table `student` ( `sno` char(9) not null, `sname` char(20) not null, `ssex` char(2) default null, `sage` smallint default null, `sdept` char(20) default null, primary key (`sno`) ) engine=innodb default charset=utf8mb4 collate=utf8mb4_0900_ai_ci | +---------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 1 row in set (0.01 sec)
3.准备备份语句,删除语句,插入测试语句
备份语句(因为备份表多一个时间戳的字段,所以备份语句要做修改一下)
mysql> show create table student_bak; +-------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | table | create table | +-------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | student_bak | create table `student_bak` ( `sno` char(9) not null, `sname` char(20) not null, `ssex` char(2) default null, `sage` smallint default null, `sdept` char(20) default null, `create_date` timestamp not null default current_timestamp ) engine=innodb default charset=utf8mb4 collate=utf8mb4_0900_ai_ci | +-------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 1 row in set (0.00 sec)
备份效果
插入测试语句:
insert into student values('201215124','张三','男',20,'el');
删除语句(删除数据一定要写精准了,到时候删什么,就要备份什么)
delete from student where sdept='el';
4.实际测试方案
4.1 把两条语句写进一个触发器(操作失败,逻辑执行不成功)
drop trigger if exists test_trigger; delimiter $ create trigger test_trigger after insert on student2 for each row begin insert into student_bak(sno,sname,ssex,sage,sdept) select * from student where sdept='el'; delete from student where sdept='el'; end $ delimiter ;
4.2 准备两个单独的触发器,一个是当原表出现这条数据时,插入到备份表实现备份的效果。第二个触发器是做备份表备份完数据之后,在做一个删除原表该条数据的触发器,然后实现备份完删除的效果(还是操作失败),执行报错,说的是触发器有冲突还是什么的,这样做让数据库不知道执行逻辑了。
4.3 做一个在原表如果进行删除目标数据,然后备份该条数据到备份表的触发器。最后再实现实时探测目标数据出现然后删除的操作就行了,不局限于触发器的思维,做一个定时任务就可以了(操作成功)
比如下面测试的当数据库的表中sdept字段出现了一个叫‘el'的字段时,需要把整行数据删除掉
drop trigger if exists student_bak_trigger; delimiter $ create trigger student_bak_trigger before delete on student for each row begin insert into student_bak(sno,sname,ssex,sage,sdept) select * from student where sdept='el'; end $ delimiter ;
这个触发器就实现了,如果原表的目标数据被删除了,触发器触发了就会备份该条数据
mysql> select * from student; +-----------+--------+------+------+-------+ | sno | sname | ssex | sage | sdept | +-----------+--------+------+------+-------+ | 201215121 | 李勇 | 男 | 20 | cs | | 201215122 | 刘晨 | 女 | 19 | cs | | 201215123 | 王敏 | 女 | 18 | ma | | 201215130 | 兵丁 | 男 | 20 | ch | +-----------+--------+------+------+-------+ 4 rows in set (0.00 sec) mysql> select * from student_bak; +-----------+--------+------+------+-------+---------------------+ | sno | sname | ssex | sage | sdept | create_date | +-----------+--------+------+------+-------+---------------------+ | 201215124 | 张三 | 男 | 20 | el | 2021-09-18 15:42:20 | +-----------+--------+------+------+-------+---------------------+ 1 row in set (0.00 sec) mysql> insert into student values('201215125','王五','男',30,'el'); query ok, 1 row affected (0.00 sec) mysql> select * from student; +-----------+--------+------+------+-------+ | sno | sname | ssex | sage | sdept | +-----------+--------+------+------+-------+ | 201215121 | 李勇 | 男 | 20 | cs | | 201215122 | 刘晨 | 女 | 19 | cs | | 201215123 | 王敏 | 女 | 18 | ma | | 201215125 | 王五 | 男 | 30 | el | | 201215130 | 兵丁 | 男 | 20 | ch | +-----------+--------+------+------+-------+ 5 rows in set (0.00 sec) mysql> select * from student_bak; +-----------+--------+------+------+-------+---------------------+ | sno | sname | ssex | sage | sdept | create_date | +-----------+--------+------+------+-------+---------------------+ | 201215124 | 张三 | 男 | 20 | el | 2021-09-18 15:42:20 | +-----------+--------+------+------+-------+---------------------+ 1 row in set (0.00 sec) mysql> delete from student where sdept='el'; query ok, 1 row affected (0.01 sec) mysql> select * from student_bak; +-----------+--------+------+------+-------+---------------------+ | sno | sname | ssex | sage | sdept | create_date | +-----------+--------+------+------+-------+---------------------+ | 201215124 | 张三 | 男 | 20 | el | 2021-09-18 15:42:20 | | 201215125 | 王五 | 男 | 30 | el | 2021-09-18 15:47:28 | +-----------+--------+------+------+-------+---------------------+ 2 rows in set (0.00 sec)
最后实现一个定时任务,来循环的删除一个叫‘el'的字段的整行数据,这里的定时任务是面向全局的,一定要加上数据库名和具体表名,定时任务的执行速度是可以手动调整的,下面为3s/次,以便实现需要的效果
create event if not exists e_test_event on schedule every 3 second on completion preserve do delete from abc.student where sdept='el';
关闭定时任务:
mysql> alter event e_test_event on completion preserve disable; query ok, 0 rows affected (0.00 sec)
查看定时任务:
mysql> select * from information_schema.events\g;*************************** 4. row *************************** event_catalog: def event_schema: abc event_name: e_test_event definer: root@% time_zone: system event_body: sql event_definition: delete from abc.student where sdept='el' event_type: recurring execute_at: null interval_value: 3 interval_field: second sql_mode: only_full_group_by,strict_trans_tables,no_zero_in_date,no_zero_date,error_for_division_by_zero,no_engine_substitution starts: 2021-09-17 13:35:44 ends: null status: enabled on_completion: preserve created: 2021-09-17 13:35:44 last_altered: 2021-09-17 13:35:44 last_executed: 2021-09-18 15:43:35 event_comment: originator: 3330614 character_set_client: utf8mb4 collation_connection: utf8mb4_0900_ai_ci database_collation: utf8mb4_0900_ai_ci 4 rows in set (0.00 sec)
查看触发器:
mysql> select * from information_schema.triggers\g; *************************** 5. row *************************** trigger_catalog: def trigger_schema: abc trigger_name: student_bak_trigger event_manipulation: delete event_object_catalog: def event_object_schema: abc event_object_table: student action_order: 1 action_condition: null action_statement: begin insert into student_bak(sno,sname,ssex,sage,sdept) select * from student where sdept='el'; end action_orientation: row action_timing: before action_reference_old_table: null action_reference_new_table: null action_reference_old_row: old action_reference_new_row: new created: 2021-09-18 15:41:48.53 sql_mode: only_full_group_by,strict_trans_tables,no_zero_in_date,no_zero_date,error_for_division_by_zero,no_engine_substitution definer: root@% character_set_client: utf8mb4 collation_connection: utf8mb4_0900_ai_ci database_collation: utf8mb4_0900_ai_ci 5 rows in set (0.00 sec)
实现效果:
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