推薦：mysql 查詢重復(fù)的數(shù)據(jù)的SQL優(yōu)化方案
在mysql中查詢不區(qū)分大小寫(xiě)重復(fù)的數(shù)據(jù)，往往會(huì)用到子查詢，并在子查詢中使用upper函數(shù)來(lái)將條件轉(zhuǎn)化為大寫(xiě)。如： 代碼如下: select * from staticcatalogue WHERE UPPER(Source) IN (SELECT UPPER(Source) FROM staticcatalogue GROUP BY UPPER(Source) having count(UP

 centos6.2，停止mysqld然后修改/etc/my.cnf datadir的位置，啟動(dòng)mysqld提示FAILED，查看日志

代碼如下:
120609 11:31:31 mysqld_safe mysqld from pid file /var/run/mysqld/mysqld.pid ended
120609 11:35:12 mysqld_safe Starting mysqld daemon with databases from /mnt/hgfs/mysql_data
120609 11:35:13 [Warning] Can't create test file /mnt/hgfs/mysql_data/data.lower-test
120609 11:35:13 [Warning] Can't create test file /mnt/hgfs/mysql_data/data.lower-test
/usr/libexec/mysqld: Can't change dir to '/mnt/hgfs/mysql_data/' (Errcode: 13)
120609 11:35:13 [ERROR] Aborting

 

120609 11:35:13 [Note] /usr/libexec/mysqld: Shutdown complete

120609 11:35:13 mysqld_safe mysqld from pid file /var/run/mysqld/mysqld.pid ended

新的datadir路徑確實(shí)沒(méi)問(wèn)題，而且目錄和目錄下所有文件都是777權(quán)限，上層目錄也有rx權(quán)限，只不過(guò)datadir和下屬文件owner都是root（因?yàn)槲矣锰摂M機(jī)掛載的windows的文件系統(tǒng)）。后來(lái)想到應(yīng)該是selinux搞的鬼，設(shè)置為permissive模式之后正常啟動(dòng)mysqld。

代碼如下:
[root@data selinux]# getenforce
Enforcing
[root@data selinux]# setenforce 0
[root@data selinux]# getenforce
Permissive

 

setenforce 1 設(shè)置SELinux 成為enforcing模式
setenforce 0 設(shè)置SELinux 成為permissive模式

徹底關(guān)閉，vi /etc/selinux/config 修改 SELINUX=disabled

 

代碼如下:
# This file controls the state of SELinux on the system.
# SELINUX= can take one of these three values:
#     enforcing - SELinux security policy is enforced.
#     permissive - SELinux prints warnings instead of enforcing.
#     disabled - No SELinux policy is loaded.
SELINUX=disabled
# SELINUXTYPE= can take one of these two values:
#     targeted - Targeted processes are protected,
#     mls - Multi Level Security protection.
SELINUXTYPE=targeted

分享：mysql的左右內(nèi)連接用法實(shí)例
本文實(shí)例講述了mysql的左右內(nèi)連接用法。分享給大家供大家參考。具體如下： 用個(gè)例子來(lái)解析下mysql的左連接， 右連接和內(nèi)連接 代碼如下:create table user_id ( id decimal(18) ); create table user_profile ( id decimal(18) , name varchar(255) ) ; insert into use