mysql触发器实时检测一条语句进行备份删除
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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
create table Student(Sno char(9) primary key,Sname char(20) not null,Ssex char(2),Sage smallint,Sdept char(20));
create table Course(Cno char(4) primary key,Cname char(40) not null,Cpno char(4) references Course(Cno),Ccredit smallint);
create table SC(Sno char(9),Cno char(4),Grade smallint,primary key(Sno,Cno),foreign key(Sno) references Student(Sno),foreign key (Cno) references Course(Cno));
insert into Student(Sno,Sname,Ssex,Sage,Sdept)values(\'201215121\',\'李勇\',\'男\',\'20\',\'CS\');
insert into Student(Sno,Sname,Ssex,Sage,Sdept)values(\'201215122\',\'刘晨\',\'女\',\'19\',\'CS\');
insert into Student(Sno,Sname,Ssex,Sage,Sdept)values(\'201215123\',\'王敏\',\'女\',\'18\',\'MA\');
insert into Course(Cno,Cname,Cpno,Ccredit)values(\'1\',\'数据库\',\'5\',\'4\');
insert into Course(Cno,Cname,Cpno,Ccredit)values(\'2\',\'数学\',\'null\',\'2\');
insert into Course(Cno,Cname,Cpno,Ccredit)values(\'3\',\'信息系统\',\'1\',\'4\');
insert into Course(Cno,Cname,Cpno,Ccredit)values(\'4\',\'操作系统\',\'6\',\'3\');
insert into Course(Cno,Cname,Cpno,Ccredit)values(\'5\',\'数据结构\',\'7\',\'4\');
insert into Course(Cno,Cname,Cpno,Ccredit)values(\'6\',\'数据处理\',\'null\',\'2\');
insert into Course(Cno,Cname,Cpno,Ccredit)values(\'7\',\'PASCLA语言\',\'6\',\'4\');
insert into SC(Sno,Cno,Grade)values(\'201215121\',\'1\',\'92\');
insert into SC(Sno,Cno,Grade)values(\'201215121\',\'2\',\'85\');
insert into SC(Sno,Cno,Grade)values(\'201215121\',\'3\',\'88\');
insert into SC(Sno,Cno,Grade)values(\'201215122\',\'2\',\'90\');
insert into SC(Sno,Cno,Grade)values(\'201215122\',\'3\',\'80\');
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)
修改后的备份表
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)
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)
insert into student_bak(Sno,Sname,Ssex,Sage,Sdept) select * from student where Sdept=\'MA\';
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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