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)

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)

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)

插入测试语句：

insert into student values('201215124','张三','男',20,'EL');

delete from student where Sdept='EL';

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 ;

4.3 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 ;

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)

create event if not exists e_test_eventon schedule every 3 second on completion preservedo delete from abc.student where Sdept='EL';

mysql> alter event e_test_event ON COMPLETION PRESERVE DISABLE;Query OK, 0 rows affected (0.00 sec)

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: 3330614CHARACTER_SET_CLIENT: utf8mb4COLLATION_CONNECTION: utf8mb4_0900_ai_ci  DATABASE_COLLATION: utf8mb4_0900_ai_ci4 rows in set (0.00 sec)

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: BEFOREACTION_REFERENCE_OLD_TABLE: NULLACTION_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_ci5 rows in set (0.00 sec)

现在需要实现以下需求：

解决思路：

测试方案：

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