mysql触发器实时检测一条语句进行备份删除思路详解 mysql触发器实时检测一条语句进

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

文章图片

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_triggerAFTERINSERT ON student2FOR EACH ROWBEGINinsert 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 BEGINinsert intostudent_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_eventon schedule every 3 second on completion preservedo 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: defEVENT_SCHEMA: abcEVENT_NAME: e_test_eventDEFINER: root@%TIME_ZONE: SYSTEMEVENT_BODY: SQLEVENT_DEFINITION: delete from abc.student where Sdept='EL'EVENT_TYPE: RECURRINGEXECUTE_AT: NULLINTERVAL_VALUE: 3INTERVAL_FIELD: SECONDSQL_MODE: ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTIONSTARTS: 2021-09-17 13:35:44ENDS: NULLSTATUS: ENABLEDON_COMPLETION: PRESERVECREATED: 2021-09-17 13:35:44LAST_ALTERED: 2021-09-17 13:35:44LAST_EXECUTED: 2021-09-18 15:43:35EVENT_COMMENT: ORIGINATOR: 3330614CHARACTER_SET_CLIENT: utf8mb4COLLATION_CONNECTION: utf8mb4_0900_ai_ciDATABASE_COLLATION: utf8mb4_0900_ai_ci4 rows in set (0.00 sec)

查看触发器：

mysql> select * from information_schema.triggers\G; *************************** 5. row ***************************TRIGGER_CATALOG: defTRIGGER_SCHEMA: abcTRIGGER_NAME: student_bak_triggerEVENT_MANIPULATION: DELETEEVENT_OBJECT_CATALOG: defEVENT_OBJECT_SCHEMA: abcEVENT_OBJECT_TABLE: studentACTION_ORDER: 1ACTION_CONDITION: NULLACTION_STATEMENT: BEGINinsert intostudent_bak(Sno,Sname,Ssex,Sage,Sdept) select * from student where Sdept='EL'; ENDACTION_ORIENTATION: ROWACTION_TIMING: BEFOREACTION_REFERENCE_OLD_TABLE: NULLACTION_REFERENCE_NEW_TABLE: NULLACTION_REFERENCE_OLD_ROW: OLDACTION_REFERENCE_NEW_ROW: NEWCREATED: 2021-09-18 15:41:48.53SQL_MODE: ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTIONDEFINER: root@%CHARACTER_SET_CLIENT: utf8mb4COLLATION_CONNECTION: utf8mb4_0900_ai_ciDATABASE_COLLATION: utf8mb4_0900_ai_ci5 rows in set (0.00 sec)

实现效果：