【全局變量】mysql查看全局變量以及設置全局變量的值

 

1.查看mysql的所有全局變量的值

SHOW GLOBAL VARIABLES

或者

SHOW VARIABLES

 

 

 

mysql有很多全局變量，包括系統的一些基本信息，以及mysql的一些基本配置都可以在全局變量中查到。

 

2.查看mysql的單個全局變量的值

SHOW GLOBAL VARIABLES LIKE 'wait_timeout'

或者

SELECT @@wait_timeout

 

上面的查詢也可以用模糊查詢，與上面結果一樣的模糊查詢語句

SHOW GLOBAL VARIABLES LIKE 'wait_time%'
SHOW GLOBAL VARIABLES LIKE '%wait%'

 

 

 

注意:查看mysql的全局變量也可以不加global關鍵字，例如

SHOW VARIABLES
SHOW  VARIABLES LIKE '%wait%'
SHOW  VARIABLES LIKE 'wait_timeout'
SHOW  VARIABLES LIKE '%wait%'

 

 

 

3.設置全局變量的值

 

SET GLOBAL  wait_timeout = 604800;
SET @@GLOBAL.wait_timeout = 604800

SET GLOBAL event_scheduler = ON; 
SET @@global.event_scheduler = ON; 
SET GLOBAL event_scheduler = 1; 
SET @@global.event_scheduler = 1; 

 

 

 

注意:有的時候發現修改不生效，需要關閉會話重新啟動，也就是退出一下重新登錄。但是發現重新啟動mysql服務器變量又不生效，最好的辦法就是修改mysql啟動的默認值。

(1)windows下C:\ProgramData\MySQL\MySQL Server 5.7\my.ini，在[mysqld]棧下寫下這個變量,例如修改mysql啟動后默認開啟任務調度(windows是修改my.ini文件)

　　修改:C:\ProgramData\MySQL\MySQL Server 5.7\my.ini   (注意是ProgramData目錄下的my.ini文件才能生效，如果修改C:\Program Files\MySQL\MySQL Server 5.7\my-default.ini不會生效)

[mysqld]

# Remove leading # and set to the amount of RAM for the most important data
# cache in MySQL. Start at 70% of total RAM for dedicated server, else 10%.
# innodb_buffer_pool_size = 128M

# Remove leading # to turn on a very important data integrity option: logging
# changes to the binary log between backups.
# log_bin

# These are commonly set, remove the # and set as required.
# basedir = .....
# datadir = .....
# port = .....
# server_id = .....


# Remove leading # to set options mainly useful for reporting servers.
# The server defaults are faster for transactions and fast SELECTs.
# Adjust sizes as needed, experiment to find the optimal values.
# join_buffer_size = 128M
# sort_buffer_size = 2M
# read_rnd_buffer_size = 2M 

sql_mode=NO_ENGINE_SUBSTITUTION,STRICT_TRANS_TABLES 
event_scheduler = 1

 

　　如果權限不夠不能修改參考解決辦法:http://www.cnblogs.com/qlqwjy/p/7989293.html

(2)linux下修改/etc/my.cnf,例如修改mysql默認任務調度開啟和會話時長為7天

[root@iz2ze46xi6pjjj69ailg9lz ~]# vim /etc/my.cnf