mysql觸發器實時檢測一條語句進行備份刪除

我愛睡蓮 發表於 2021-09-18
MySQL

問題描述:使用者有一個這樣一個需求,在一張表裡會不時出現 “違規” 字樣的欄位,需要在出現這個欄位的時候,把整行的資料刪掉。這是個採集任務,如果發現有“違規”字樣的資料,會整點或者什麼時間進行統一上報,也無法對源頭進行控制讓這種資料不生成。

現在需要實現以下需求:1.實時檢測這條資料的產生,發現後刪除

                                        2.在刪除之前作備份這條資料

 

解決思路:需要明確解決思路,

                  1.首先是如何實時探測刪除?詢問開發,這條資料的生成方式為insert,就可以做一個當表做插入的時候,然後做一個after insert 做delete資料的觸發器

                  2.如何進行備份?何種方式備份?能不能備份到一個表裡,這個表裡記錄每次插入的時間,建立這個備份表可以取與原表結構基本相同,但是備份表要刪除原表的自增屬性,主鍵,外來鍵等屬性,新增一個時間戳欄位,方便記錄每次備份資料的時間,刪除以上屬性是為了能夠把資料寫入備份表中

                  3.如何在刪除之前做備份呢?一開始想的是放到一個觸發器就行,先把資料進行備份,然後後面跟著一條刪除,測試的時候行不通

 

測試方案:先準備一些測試資料和測試表

1.建立測試資料

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','劉晨','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','資料庫','5','4');
insert into Course(Cno,Cname,Cpno,Ccredit)values('2','數學','null','2');
insert into Course(Cno,Cname,Cpno,Ccredit)values('3','資訊系統','1','4');
insert into Course(Cno,Cname,Cpno,Ccredit)values('4','作業系統','6','3');
insert into Course(Cno,Cname,Cpno,Ccredit)values('5','資料結構','7','4');
insert into Course(Cno,Cname,Cpno,Ccredit)values('6','資料處理','null','2');
insert into Course(Cno,Cname,Cpno,Ccredit)values('7','PASCLA語言','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.建立備份表。檢視建表語句,正式環境是不知道原表的表結構的,需要有改原表結構,並建立新備份表的操作的

原表建表語句

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)

修改後的備份表


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.準備備份語句,刪除語句,插入測試語句

備份語句(因為備份表多一個時間戳的欄位,所以備份語句要做修改一下)

insert into  student_bak(Sno,Sname,Ssex,Sage,Sdept) select * from student where Sdept='MA'; 

備份效果

mysql觸發器實時檢測一條語句進行備份刪除

 

插入測試語句:

insert into student values('201215124','張三','',20,'EL');

刪除語句(刪除資料一定要寫精準了,到時候刪什麼,就要備份什麼)

delete from student where Sdept='EL';

 

4.實際測試方案

4.1 把兩條語句寫進一個觸發器(操作失敗,邏輯執行不成功)

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 準備兩個單獨的觸發器,一個是當原表出現這條資料時,插入到備份表實現備份的效果。第二個觸發器是做備份表備份完資料之後,在做一個刪除原表該條資料的觸發器,然後實現備份完刪除的效果(還是操作失敗),執行報錯,說的是觸發器有衝突還是什麼的,這樣做讓資料庫不知道執行邏輯了。

4.3 做一個在原表如果進行刪除目標資料,然後備份該條資料到備份表的觸發器。最後再實現實時探測目標資料出現然後刪除的操作就行了,不侷限於觸發器的思維,做一個定時任務就可以了(操作成功)

比如下面測試的當資料庫的表中Sdept欄位出現了一個叫‘EL’的欄位時,需要把整行資料刪除掉

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 ;

這個觸發器就實現了,如果原表的目標資料被刪除了,觸發器觸發了就會備份該條資料

mysql> select * from student;
+-----------+--------+------+------+-------+
| Sno       | Sname  | Ssex | Sage | Sdept |
+-----------+--------+------+------+-------+
| 201215121 | 李勇   | 男   |   20 | CS    |
| 201215122 | 劉晨   | 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 | 張三   | 男   |   20 | EL    | 2021-09-18 15:42:20 |
+-----------+--------+------+------+-------+---------------------+
1 row in set (0.00 sec)

mysql> insert into student values('201215125','王五','',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 | 劉晨   | 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 | 張三   | 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 | 張三   | 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)

最後實現一個定時任務,來迴圈的刪除一個叫‘EL’的欄位的整行資料,這裡的定時任務是面向全域性的,一定要加上資料庫名和具體表名,定時任務的執行速度是可以手動調整的,下面為3s/次,以便實現需要的效果

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

關閉定時任務:

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

檢視定時任務:

mysql> select * from information_schema.events\G;
*************************** 4. row *************************** EVENT_CATALOG: def EVENT_SCHEMA: abc EVENT_NAME: e_test_event DEFINER: [email protected]% 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)

檢視觸發器:

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: [email protected]%
      CHARACTER_SET_CLIENT: utf8mb4
      COLLATION_CONNECTION: utf8mb4_0900_ai_ci
        DATABASE_COLLATION: utf8mb4_0900_ai_ci
5 rows in set (0.00 sec)

 

實現效果:

mysql觸發器實時檢測一條語句進行備份刪除