nba买球(014)mysql中的事件

作者:计算机教程

nba买球,mysql学习记录(十一)--事件调度器

一、理论:

1.优势:
1)减少系统管理员的操作风险,有利于数据库整体迁移。因数据库迁移时即可同时迁移调度事件
2.场景:
1)定期收集统计信息
2)清理历史数据
3)数据库检查
3.要点:
1)在性能要求高且重要的数据库中要慎重部署和启用调度器
2)过于复杂的更适合用程序
3)开启和关闭事件调度器需要具有超级用户权限

二、实践:

 

mysql> use test1;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed
mysql> create table test(id1 varchar(10),create_time datetime);
Query OK, 0 rows affected (0.02 sec)

mysql> create event test_event_1
    -> on schedule
    -> every 5 second 
    -> do 
    -> insert into test1.test(id1,create_time)
    -> values ('test',now());
Query OK, 0 rows affected (0.01 sec)

mysql> show events G;
*************************** 1. row ***************************
                  Db: test1
                Name: test_event_1
             Definer: [email protected]
           Time zone: SYSTEM
                Type: RECURRING
          Execute at: NULL
      Interval value: 5
      Interval field: SECOND
              Starts: 2015-10-14 06:33:17
                Ends: NULL
              Status: ENABLED
          Originator: 1
character_set_client: utf8
collation_connection: utf8_general_ci
  Database Collation: utf8_general_ci
1 row in set (0.01 sec)

ERROR: 
No query specified

mysql> select * from test;
Empty set (0.00 sec)

mysql> show variables like '%scheduler%';
 ----------------- ------- 
| Variable_name   | Value |
 ----------------- ------- 
| event_scheduler | OFF   |
 ----------------- ------- 
1 row in set (0.00 sec)

mysql> set global event_scheduler = 1 ;
Query OK, 0 rows affected (0.00 sec)

mysql> show variables like '%scheduler%';
 ----------------- ------- 
| Variable_name   | Value |
 ----------------- ------- 
| event_scheduler | ON    |
 ----------------- ------- 
1 row in set (0.00 sec)

mysql> show processlist G;
*************************** 1. row ***************************
     Id: 17
   User: root
   Host: localhost
     db: test1
Command: Sleep
   Time: 247901
  State: 
   Info: NULL
*************************** 2. row ***************************
     Id: 21
   User: root
   Host: localhost
     db: test1
Command: Query
   Time: 0
  State: NULL
   Info: show processlist
*************************** 3. row ***************************
     Id: 22
   User: event_scheduler
   Host: localhost
     db: NULL
Command: Daemon
   Time: 1
  State: Waiting for next activation
   Info: NULL
3 rows in set (0.00 sec)

ERROR: 
No query specified

mysql> select * from test;
 ------ --------------------- 
| id1  | create_time         |
 ------ --------------------- 
| test | 2015-10-14 06:33:57 |
| test | 2015-10-14 06:34:02 |
| test | 2015-10-14 06:34:07 |
| test | 2015-10-14 06:34:12 |
| test | 2015-10-14 06:34:17 |
| test | 2015-10-14 06:34:22 |
 ------ --------------------- 
6 rows in set (0.00 sec)

mysql> create event trunc_test
    -> on schedule every 1 minute
    -> do truncate table test;
Query OK, 0 rows affected (0.00 sec)

mysql> select * from test;
 ------ --------------------- 
| id1  | create_time         |
 ------ --------------------- 
| test | 2015-10-14 06:34:52 |
| test | 2015-10-14 06:34:57 |
| test | 2015-10-14 06:35:02 |
| test | 2015-10-14 06:35:07 |
| test | 2015-10-14 06:35:12 |
| test | 2015-10-14 06:35:17 |
| test | 2015-10-14 06:35:22 |
| test | 2015-10-14 06:35:27 |
| test | 2015-10-14 06:35:32 |
| test | 2015-10-14 06:35:37 |
 ------ --------------------- 
10 rows in set (0.00 sec)

mysql> select * from test;
 ------ --------------------- 
| id1  | create_time         |
 ------ --------------------- 
| test | 2015-10-14 06:37:52 |
| test | 2015-10-14 06:37:57 |
 ------ --------------------- 
2 rows in set (0.00 sec)

mysql> show processlist G;
*************************** 1. row ***************************
     Id: 17
   User: root
   Host: localhost
     db: test1
Command: Sleep
   Time: 248177
  State: 
   Info: NULL
*************************** 2. row ***************************
     Id: 21
   User: root
   Host: localhost
     db: test1
Command: Query
   Time: 0
  State: NULL
   Info: show processlist
*************************** 3. row ***************************
     Id: 22
   User: event_scheduler
   Host: localhost
     db: NULL
Command: Daemon
   Time: 2
  State: Waiting for next activation
   Info: NULL
3 rows in set (0.00 sec)

ERROR: 
No query specified

mysql> alter event trunc_test disable;
Query OK, 0 rows affected (0.02 sec)

mysql> select * from test;
 ------ --------------------- 
| id1  | create_time         |
 ------ --------------------- 
| test | 2015-10-14 06:38:52 |
| test | 2015-10-14 06:38:57 |
| test | 2015-10-14 06:39:02 |
| test | 2015-10-14 06:39:07 |
| test | 2015-10-14 06:39:12 |
| test | 2015-10-14 06:39:17 |
| test | 2015-10-14 06:39:22 |
| test | 2015-10-14 06:39:27 |
| test | 2015-10-14 06:39:32 |
| test | 2015-10-14 06:39:37 |
 ------ --------------------- 
10 rows in set (0.00 sec)

mysql> select * from test;
 ------ --------------------- 
| id1  | create_time         |
 ------ --------------------- 
| test | 2015-10-14 06:38:52 |
| test | 2015-10-14 06:38:57 |
| test | 2015-10-14 06:39:02 |
| test | 2015-10-14 06:39:07 |
| test | 2015-10-14 06:39:12 |
| test | 2015-10-14 06:39:17 |
| test | 2015-10-14 06:39:22 |
| test | 2015-10-14 06:39:27 |
| test | 2015-10-14 06:39:32 |
| test | 2015-10-14 06:39:37 |
| test | 2015-10-14 06:39:42 |
| test | 2015-10-14 06:39:47 |
| test | 2015-10-14 06:39:52 |
| test | 2015-10-14 06:39:57 |
| test | 2015-10-14 06:40:02 |
| test | 2015-10-14 06:40:07 |
 ------ --------------------- 
16 rows in set (0.00 sec)

mysql> alter event test_event_1 disable;
Query OK, 0 rows affected (0.00 sec)

mysql> select * from test;
 ------ --------------------- 
| id1  | create_time         |
 ------ --------------------- 
| test | 2015-10-14 06:38:52 |
| test | 2015-10-14 06:38:57 |
| test | 2015-10-14 06:39:02 |
| test | 2015-10-14 06:39:07 |
| test | 2015-10-14 06:39:12 |
| test | 2015-10-14 06:39:17 |
| test | 2015-10-14 06:39:22 |
| test | 2015-10-14 06:39:27 |
| test | 2015-10-14 06:39:32 |
| test | 2015-10-14 06:39:37 |
| test | 2015-10-14 06:39:42 |
| test | 2015-10-14 06:39:47 |
| test | 2015-10-14 06:39:52 |
| test | 2015-10-14 06:39:57 |
| test | 2015-10-14 06:40:02 |
| test | 2015-10-14 06:40:07 |
| test | 2015-10-14 06:40:12 |
| test | 2015-10-14 06:40:17 |
| test | 2015-10-14 06:40:22 |
| test | 2015-10-14 06:40:27 |
 ------ --------------------- 
20 rows in set (0.00 sec)

mysql>  drop event test_event_1;
Query OK, 0 rows affected (0.01 sec)

mysql> show events G;
*************************** 1. row ***************************
                  Db: test1
                Name: trunc_test
             Definer: [email protected]
           Time zone: SYSTEM
                Type: RECURRING
          Execute at: NULL
      Interval value: 1
      Interval field: MINUTE
              Starts: 2015-10-14 06:34:48
                Ends: NULL
              Status: DISABLED
          Originator: 1
character_set_client: utf8
collation_connection: utf8_general_ci
  Database Collation: utf8_general_ci
1 row in set (0.00 sec)

ERROR: 
No query specified

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概述

事件调度器是MySQL5.1后新增的功能,可以将数据库按自定义的时间周期触发某种操作,可以理解为时间触发器,类似于linux系统下面的任务调度器crontab,或者类似与window下面的计划任务。值得一提的是MySQL的事件调度器可以精确到每秒钟执行一个任务,而操作系统的计划任务(如:Linux下的CRON或Windows下的任务计划)只能精确到每分钟执行一次。

查看事件功能是否开启

在使用事件这个功能,首先要保证你的mysql的版本是5.1以上,然后还要查看你的mysql服务器上的事件是否开启。
查看事件是否开启,使用如下命令查看:

#方式一
SHOW VARIABLES LIKE 'event_scheduler';
#方式二
SELECT @@event_scheduler;
#方式三
SHOW PROCESSLIST;

#查看事件状态
SHOW EVENTS;

如果看到event_scheduler为on或者PROCESSLIST中显示有event_scheduler的信息说明就已经开启了事件。如果显示为off或者在PROCESSLIST中查看不到event_scheduler的信息,那么就说明事件没有开启,我们需要开启它。

开启事件功能

方式一、通过动态参数修改

SET GLOBAL event_scheduler = ON;

更改完这个参数就立刻生效了,但是重启mysql又还原了,即设置不能跨重启。
方式二、更改配置文件然后重启
在my.cnf中的[mysqld]部分添加如下内容,然后重启mysql。

event_scheduler=ON;

一劳永逸,需要能够修改数据库配置的权限。

方式三、直接在启动命令加上“–event_scheduler=1”

mysqld ... --event_scheduler=ON

事件的语法

1. 创建事件

CREATE
    [DEFINER = { user | CURRENT_USER }]
    EVENT
    [IF NOT EXISTS]
    event_name
    ON SCHEDULE schedule
    [ON COMPLETION [NOT] PRESERVE]
    [ENABLE | DISABLE | DISABLE ON SLAVE]
    [COMMENT 'comment']
    DO event_body;

schedule:
    AT timestamp [  INTERVAL interval] ...
     | EVERY interval
    [STARTS timestamp [  INTERVAL interval] ...]
    [ENDS timestamp [  INTERVAL interval] ...]
interval:
  quantity {YEAR | QUARTER | MONTH | DAY | HOUR | MINUTE |
              WEEK | SECOND | YEAR_MONTH | DAY_HOUR |
DAY_MINUTE |DAY_SECOND | HOUR_MINUTE |
HOUR_SECOND | MINUTE_SECOND}

DEFINER: 定义事件执行的时候检查权限的用户。
ON SCHEDULE schedule: 定义执行的时间和时间间隔。
ON COMPLETION [NOT] PRESERVE: 定义事件是一次执行还是永久执行,默认为一次执行,即NOT PRESERVE。
ENABLE | DISABLE | DISABLE ON SLAVE: 定义事件创建以后是开启还是关闭,以及在从上关闭。如果是从服务器自动同步主上的创建事件的语句的话,会自动加上DISABLE ON SLAVE。
COMMENT 'comment': 定义事件的注释。

2. 更改事件

ALTER
    [DEFINER = { user | CURRENT_USER }]
    EVENT event_name
    [ON SCHEDULE schedule]
    [ON COMPLETION [NOT] PRESERVE]
    [RENAME TO new_event_name]
    [ENABLE | DISABLE | DISABLE ON SLAVE]
    [COMMENT 'comment']
    [DO event_body]

3. 删除事件的语法

DROP EVENT [IF EXISTS] event_name;

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