部署tomcat单机多实例，keepalived+mysql的互为主从高可用，mysql+keepalived高可用

2023-12-23 12:52
文章标签 mysql 部署 tomcat 实例 可用 database 单机 为主 keepalived

本文主要是介绍部署tomcat单机多实例，keepalived+mysql的互为主从高可用，mysql+keepalived高可用，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

部署tomcat单机多实例

在Tomcat中部署单机多实例是一种常见的做法，它允许您在同一台服务器上运行多个独立的Tomcat实例，每个实例都有自己的配置、日志和应用程序。

安装jdk环境

首先配置java环境
[root@tomcat ~]# tar xf  jdk-8u211-linux-x64.tar.gz -C /usr/local改名，设置环境变量
[root@tomcat ~]# cd /usr/local
[root@tomcat local]# mv jdk1.8.0_211/ java
[root@tomcat local]# vim  /etc/profile.d/java.shJAVA_HOME=/usr/local/java
PATH=$PATH:$JAVA_HOME/bin重载环境变量
[root@tomcat local]# source /etc/profile.d/java.sh 
查看jdk是否安装成功
[root@tomcat local]# java -version
java version "1.8.0_211"
Java(TM) SE Runtime Environment (build 1.8.0_211-b12)
Java HotSpot(TM) 64-Bit Server VM (build 25.211-b12, mixed mode)

安装tomcat

解压 
[root@tomcat ~]# tar xf apache-tomcat-8.5.92.tar.gz -C /usr/local进入
[root@tomcat ~]# cd /usr/local
改名
[root@tomcat local]# mv  apache-tomcat-8.5.92 tomcat复制
[root@tomcat local]# cp -r tomcat tomcat-2
[root@tomcat local]# cp -r tomcat tomcat-3

配置文件

tomcat

修改配置文件
tomcat
[root@tomcat local]# vim ./tomcat/conf/server.xml

tomcat-2

[root@tomcat local]# vim ./tomcat-2/conf/server.xml

tomcat-3

[root@tomcat local]# vim ./tomcat-3/conf/server.xml

启动tomcat

[root@tomcat local]# ./tomcat/bin/startup.sh 
Using CATALINA_BASE:   /usr/local/tomcat
Using CATALINA_HOME:   /usr/local/tomcat
Using CATALINA_TMPDIR: /usr/local/tomcat/temp
Using JRE_HOME:        /usr/local/java
Using CLASSPATH:       /usr/local/tomcat/bin/bootstrap.jar:/usr/local/tomcat/bin/tomcat-juli.jar
Using CATALINA_OPTS:   
Tomcat started.[root@tomcat local]# ./tomcat-2/bin/startup.sh 
Using CATALINA_BASE:   /usr/local/tomcat-2
Using CATALINA_HOME:   /usr/local/tomcat-2
Using CATALINA_TMPDIR: /usr/local/tomcat-2/temp
Using JRE_HOME:        /usr/local/java
Using CLASSPATH:       /usr/local/tomcat-2/bin/bootstrap.jar:/usr/local/tomcat-2/bin/tomcat-juli.jar
Using CATALINA_OPTS:   
Tomcat started.[root@tomcat local]# ./tomcat-3/bin/startup.sh 
Using CATALINA_BASE:   /usr/local/tomcat-3
Using CATALINA_HOME:   /usr/local/tomcat-3
Using CATALINA_TMPDIR: /usr/local/tomcat-3/temp
Using JRE_HOME:        /usr/local/java
Using CLASSPATH:       /usr/local/tomcat-3/bin/bootstrap.jar:/usr/local/tomcat-3/bin/tomcat-juli.jar
Using CATALINA_OPTS:   
Tomcat started.

查看端口

[root@tomcat local]# ss -nplt
State       Recv-Q Send-Q                                        Local Address:Port                                                       Peer Address:Port              
LISTEN      0      128                                                       *:22                                                                    *:*                   users:(("sshd",pid=920,fd=3))
LISTEN      0      100                                               127.0.0.1:25                                                                    *:*                   users:(("master",pid=1148,fd=13))
LISTEN      0      1                                        [::ffff:127.0.0.1]:8005                                                               [::]:*                   users:(("java",pid=1902,fd=61))
LISTEN      0      1                                        [::ffff:127.0.0.1]:8006                                                               [::]:*                   users:(("java",pid=2043,fd=61))
LISTEN      0      1                                        [::ffff:127.0.0.1]:8007                                                               [::]:*                   users:(("java",pid=2095,fd=61))
LISTEN      0      80                                                     [::]:3306                                                               [::]:*                   users:(("mysqld",pid=1004,fd=29))
LISTEN      0      100                                                    [::]:8080                                                               [::]:*                   users:(("java",pid=1902,fd=52))
LISTEN      0      100                                                    [::]:8081                                                               [::]:*                   users:(("java",pid=2043,fd=52))
LISTEN      0      100                                                    [::]:8082                                                               [::]:*                   users:(("java",pid=2095,fd=52))
LISTEN      0      128

访问实例

keepalived+mysql互为主从的高可用

IP1：10.36.192.223 安装msyql

IP2：10.36.192.222 安装mysql

首先做IP1为主，IP2为从

IP1的操作

IP1的操作
[root@IP1 ~]# mkdir /var/log/mysql
[root@IP1 ~]# chown  -R mysql.mysql /var/log/mysqlvim /etc/my.cnf
###
log-bin=/var/log/mysql/mysql-bin       #启用二进制文件日志记录
server-id=1 
###
重启mysql
# systemctl restart mysqld

登录数据库
创建主从登录的用户
mysql> grant replication slave on *.* to  'zc'@'%' identified by 'Qianfeng@123';刷新
mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)查看二进制日志
mysql> show master status;
+------------------+----------+--------------+------------------+-------------------+
| File             | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+------------------+----------+--------------+------------------+-------------------+
| mysql-bin.000001 |      587 |              |                  |                   |
+------------------+----------+--------------+------------------+-------------------+
1 row in set (0.00 sec)

IP2的操作

[root@IP2 ~]# mkdir /var/log/mysql
[root@IP2 ~]# chown  -R mysql.mysql /var/log/mysqlvim /etc/my.cnf
###
server-id=2重启msyql
# systemctl restart mysqld
登录数据库
mysql> CHANGE MASTER TO->   MASTER_HOST='10.36.192.223',->   MASTER_USER='zc',->   MASTER_PASSWORD='Qianfeng@123',->   MASTER_PORT=3306,->   MASTER_LOG_FILE='mysql-bin.000001',->   MASTER_LOG_POS=587,->   MASTER_CONNECT_RETRY=10;
Query OK, 0 rows affected, 2 warnings (0.01 sec)mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)启动主从，查看主从状态
mysql> start slave;
Query OK, 0 rows affected (0.00 sec)mysql> show slave status\G;
*************************** 1. row ***************************Slave_IO_State: Waiting for master to send eventMaster_Host: 10.36.192.223Master_User: zcMaster_Port: 3306Connect_Retry: 10Master_Log_File: mysql-bin.000001Read_Master_Log_Pos: 587Relay_Log_File: slave-relay-bin.000002Relay_Log_Pos: 320Relay_Master_Log_File: mysql-bin.000001Slave_IO_Running: YesSlave_SQL_Running: Yes

做IP2为主，IP1为从

IP2的操作

vim /etc/my.cnf
###
添加第二行
[mysqld]
log-bin=/var/log/mysql/mysql-bin       #启用二进制文件日志记录重启mysql
# systemctl restart mysqld登录数据库创建主从登录的用户
mysql> grant replication slave on *.* to  'zxd'@'%' identified by 'Qianfeng@123';
Query OK, 0 rows affected, 1 warning (0.00 sec)mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)查看二进制日志坐标
mysql> show master status;
+------------------+----------+--------------+------------------+-------------------+
| File             | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+------------------+----------+--------------+------------------+-------------------+
| mysql-bin.000001 |      154 |              |                  |                   |
+------------------+----------+--------------+------------------+-------------------+
1 row in set (0.00 sec)

IP1的操作

mysql> CHANGE MASTER TO->   MASTER_HOST='10.36.192.222',->   MASTER_USER='zxd',->   MASTER_PASSWORD='Qianfeng@123',->   MASTER_PORT=3306,->   MASTER_LOG_FILE='mysql-bin.000001',->   MASTER_LOG_POS=154,->   MASTER_CONNECT_RETRY=10;
Query OK, 0 rows affected, 2 warnings (0.01 sec)刷新
mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)启动主从
mysql> start slave;
Query OK, 0 rows affected (0.00 sec)查看主从状态
mysql> show slave status\G;
*************************** 1. row ***************************Slave_IO_State: Waiting for master to send eventMaster_Host: 10.36.192.222Master_User: zxdMaster_Port: 3306Connect_Retry: 10Master_Log_File: mysql-bin.000001Read_Master_Log_Pos: 154Relay_Log_File: master-relay-bin.000002Relay_Log_Pos: 320Relay_Master_Log_File: mysql-bin.000001Slave_IO_Running: YesSlave_SQL_Running: Yes

互为主从成功配置

在IP1的数据库创库，IP2也可以看到

IP1
mysql> create database zhangxiaodong;
Query OK, 1 row affected (0.00 sec)mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
| zhangxiaodong      |
+--------------------+
5 rows in set (0.00 sec)IP2
mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
| zhangxiaodong      |
+--------------------+
5 rows in set (0.00 sec)

安装keepalived

IP1  IP2都操作
# yum -y install keepalived

编写当某一台的MySQL停掉以后，就自动停掉那台机器的keepalived服务的脚本

cd /etc/keepalived
[root@IP1 keepalived]# cat keepalived_check_mysql.sh 
#!/bin/bash
/usr/bin/mysql -uroot -p'Qianfeng@123' -e "show status" &>/dev/null
if [ $? -ne 0 ] ;then
#	service keepalived stopsystemctl stop keepalived
ficd /etc/keepalived
[root@IP2 keepalived]# cat keepalived_check_mysql.sh 
#!/bin/bash
/usr/bin/mysql -uroot -p'Qianfeng@123' -e "show status" &>/dev/null
if [ $? -ne 0 ] ;then
#	service keepalived stopsystemctl stop keepalived
fi

给脚本执行权限

chmod a+x keepalived_check_mysql.sh

在keepalived的配置文件中引用脚本

IP1
[root@IP1  keepalived]# cat keepalived.conf 
! Configuration File for keepalivedglobal_defs {router_id directory1 
}
vrrp_script check_run {script "/etc/keepalived/keepalived_check_mysql.sh"interval 5
}vrrp_instance VI_1 {state MASTERinterface ens33virtual_router_id 66priority 100advert_int 1authentication {auth_type PASSauth_pass 1111}virtual_ipaddress {10.36.192.233/24}track_script {check_run}
}
IP2
[root@IP2 keepalived]# cat keepalived.conf 
! Configuration File for keepalivedglobal_defs {router_id directory2
}
vrrp_script check_run {script "/etc/keepalived/keepalived_check_mysql.sh"interval 5
}vrrp_instance VI_1 {state BACKUPnopreemptinterface ens33virtual_router_id 66priority 50advert_int 1authentication {auth_type PASSauth_pass 1111}virtual_ipaddress {10.36.192.233/24}track_script {#check_runcheck_run}
}

启动keepqlived

#systemctl start keepalived

[root@IP1 keepalived]# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00inet 127.0.0.1/8 scope host lovalid_lft forever preferred_lft foreverinet6 ::1/128 scope host valid_lft forever preferred_lft forever
2: ens33: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000link/ether 00:0c:29:99:b8:b4 brd ff:ff:ff:ff:ff:ffinet 10.36.192.223/24 brd 10.36.192.255 scope global noprefixroute dynamic ens33valid_lft 255232sec preferred_lft 255232secinet 10.36.192.233/24 scope global secondary ens33valid_lft forever preferred_lft forever

此时的虚拟IP为10.36.192.233，在IP1上，但由于互为主从，因此查到数据相同

在那俩台数据库都创建可以允许远程登录数据库的用户

IP1
mysql> grant all on *.* to 'malong'@'%' identified by 'Qianfeng@123!';
Query OK, 0 rows affected, 1 warning (0.00 sec)IP2
mysql> grant all on *.* to 'malong'@'%' identified by 'Qianfeng@123!';
Query OK, 0 rows affected, 1 warning (0.00 sec)

准备另一台机器，做测试实验

[root@mysql ~]# mysql -umalong -pQianfeng@123! -h10.36.192.233 
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 15
Server version: 5.7.42-log MySQL Community Server (GPL)Copyright (c) 2000, 2023, Oracle and/or its affiliates.Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
| zhangxiaodong      |
+--------------------+
5 rows in set (0.00 sec)

经过测试发现，当IP1的数据库停掉以后，keepalived也会停掉，此时虚拟IP会飘向IP2的机器上，但是由于俩台数据库是互为主从，因此测试机器登上去查看到的数据是相同的.这样可以保证数据库的高可用.

MySQL+keepalived高可用

实验机器IP
master（干净机器）10.36.192.223        
slave （干净机器）10.36.192.222
测试（已有MySQL）10.36.192.199

俩台服务器都安装mysql，keepalived，并修改mysql初始密码

[root@master ~]# yum install -y mysql-server keepalived[root@master ~]# systemctl restart mysqld[root@master ~]# grep "password" /var/log/mysqld.log2023-11-02T07:46:28.937422Z 1 [Note] A temporary password is generated for root@localhost: fB#sVi1UyRW;[root@master ~]# mysqladmin -uroot -p'fB#sVi1UyRW;' password 'Qianfeng@123'
[root@slave ~]# yum install -y mysql-server keepalived[root@slave ~]# systemctl restart mysqld[root@slave ~]# grep "password" /var/log/mysqld.log2023-11-02T07:46:28.937422Z 1 [Note] A temporary password is generated for root@localhost: ?Huo=g>tQ9tn;[root@slave ~]# mysqladmin -uroot -p'?Huo=g>tQ9tn' password 'Qianfeng@123'

登录俩台数据库创建允许远程登录的用户

[root@master ~]# mysql -uroot -p'Qianfeng@123'
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 5
...mysql> grant all on *.* to 'malong'@'%' identified by 'Qianfeng@123!';
Query OK, 0 rows affected, 1 warning (0.00 sec)mysql> \q
Bye[root@slave ~]# mysql -uroot -p'Qianfeng@123'
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 5
...mysql> grant all on *.* to 'malong'@'%' identified by 'Qianfeng@123!';
Query OK, 0 rows affected, 1 warning (0.00 sec)mysql> \q
Bye

在master的数据库创建一个库

create database dbtest；

master配置keepalived

[root@master ~]# vim /etc/keepalived/keepalived.conf
! Configuration File for keepalivedglobal_defs {router_id directory1 
}
vrrp_instance VI_1 {state MASTERinterface ens33virtual_router_id 66priority 100advert_int 1authentication {auth_type PASSauth_pass 1111}virtual_ipaddress {10.36.192.233/24   ###虚拟的IP}
}

slave配置keepalived

[root@slave ~]# vim /etc/keepalived/keepalived.conf
! Configuration File for keepalived
global_defs {router_id directory2
}
vrrp_instance VI_1 {state BACKUPnopreemptinterface ens33virtual_router_id 66priority 50advert_int 1authentication {auth_type PASSauth_pass 1111}virtual_ipaddress {10.36.192.233/24}
}

配置数据库检查脚本

[root@master keepalived]# cat keepalived_check_mysql.sh 
#!/bin/bash
/usr/bin/mysql -uroot -p'Qianfeng@123' -e "show status" &>/dev/null
if [ $? -ne 0 ] ;then
#	service keepalived stopsystemctl stop keepalived
fi[root@slave keepalived]# cat keepalived_check_mysql.sh 
#!/bin/bash
/usr/bin/mysql -uroot -p'Qianfeng@123' -e "show status" &>/dev/null
if [ $? -ne 0 ] ;then
#	service keepalived stopsystemctl stop keepalived
fi

记得给脚本执行权限

chmod a+x keepalived_check_mysql.sh

在配置文件中引用脚本

[root@master  keepalived]# cat keepalived.conf 
! Configuration File for keepalivedglobal_defs {router_id directory1 
}
vrrp_script check_run {script "/etc/keepalived/keepalived_check_mysql.sh"interval 5
}vrrp_instance VI_1 {state MASTERinterface ens33virtual_router_id 66priority 100advert_int 1authentication {auth_type PASSauth_pass 1111}virtual_ipaddress {10.36.192.233/24}track_script {check_run}
}

[root@slave keepalived]# cat keepalived.conf 
! Configuration File for keepalivedglobal_defs {router_id directory2
}
vrrp_script check_run {script "/etc/keepalived/keepalived_check_mysql.sh"interval 5
}vrrp_instance VI_1 {state BACKUPnopreemptinterface ens33virtual_router_id 66priority 50advert_int 1authentication {auth_type PASSauth_pass 1111}virtual_ipaddress {10.36.192.233/24}track_script {#check_runcheck_run}
}

启动keepalived

systemctl start keepalived

在master端查看到虚拟IP

[root@master ~]# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00inet 127.0.0.1/8 scope host lovalid_lft forever preferred_lft foreverinet6 ::1/128 scope host valid_lft forever preferred_lft forever
2: ens33: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000link/ether 00:0c:29:99:b8:b4 brd ff:ff:ff:ff:ff:ffinet 10.36.192.223/24 brd 10.36.192.255 scope global noprefixroute dynamic ens33valid_lft 250228sec preferred_lft 250228secinet 10.36.192.233/24 scope global secondary ens33valid_lft forever preferred_lft forever

在测试机器测试

[root@mysql ~]# mysql -umalong -pQianfeng@123! -h10.36.192.233 
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 635
Server version: 5.7.42 MySQL Community Server (GPL)Copyright (c) 2000, 2023, Oracle and/or its affiliates.Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| dbtest             |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
5 rows in set (0.00 sec)

此时查看的是master端的数据库

停掉master端的msyql

[root@master ~]# systemctl stop mysqld[root@master ~]# systemctl status keepalived
● keepalived.service - LVS and VRRP High Availability MonitorLoaded: loaded (/usr/lib/systemd/system/keepalived.service; disabled; vendor preset: disabled)Active: inactive (dead)此时的虚拟ip在slave端
[root@slave ~]# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00inet 127.0.0.1/8 scope host lovalid_lft forever preferred_lft foreverinet6 ::1/128 scope host valid_lft forever preferred_lft forever
2: ens33: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000link/ether 00:0c:29:9f:83:60 brd ff:ff:ff:ff:ff:ffinet 10.36.192.222/24 brd 10.36.192.255 scope global noprefixroute dynamic ens33valid_lft 258272sec preferred_lft 258272secinet 10.36.192.233/24 scope global secondary ens33valid_lft forever preferred_lft forever

使用测试机子登录远程MySQL

[root@mysql ~]# mysql -umalong -pQianfeng@123! -h10.36.192.233 -P 3306
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or \g.
...
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
4 rows in set (0.01 sec)

此时查看到的是slave机器的数据库

此时先启动master端的数据库，与keepalived，顺序不能乱

[root@master ~]# systemctl start mysqld
[root@master ~]# systemctl start keepalived查看此时的虚拟IP 在master端上
[root@master ~]# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00inet 127.0.0.1/8 scope host lovalid_lft forever preferred_lft foreverinet6 ::1/128 scope host valid_lft forever preferred_lft forever
2: ens33: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000link/ether 00:0c:29:99:b8:b4 brd ff:ff:ff:ff:ff:ffinet 10.36.192.223/24 brd 10.36.192.255 scope global noprefixroute dynamic ens33valid_lft 257980sec preferred_lft 257980secinet 10.36.192.233/24 scope global secondary ens33valid_lft forever preferred_lft forever

测试机查看到数据库此时是master端的数据库

[root@mysql ~]# mysql -umalong -pQianfeng@123! -h10.36.192.233 -P 3306
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or \g.
...
mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| dbtest             |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
5 rows in set (0.01 sec)

也就是当master，slave端的MySQL与keepalived同时开启时，虚拟IP会在master端，此时测试机远程登录的MySQL也是master端的

当master端的MySQL与keepalived停掉后，虚拟IP会飘向slave端，此时测试机远程登录的MySQL是slave端的。

这篇关于部署tomcat单机多实例，keepalived+mysql的互为主从高可用，mysql+keepalived高可用的文章就介绍到这儿，希望我们推荐的文章对编程师们有所帮助！


http://www.chinasem.cn/article/528109。

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Python开发文字版随机事件游戏的项目实例

Python开发文字版随机事件游戏的项目实例

《Python开发文字版随机事件游戏的项目实例》随机事件游戏是一种通过生成不可预测的事件来增强游戏体验的类型,在这篇博文中,我们将使用Python开发一款文字版随机事件游戏,通过这个项目,读者不仅能够... 目录项目概述2.1 游戏概念2.2 游戏特色2.3 目标玩家群体技术选择与环境准备3.1 开发环境3
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MySQL数据库约束深入详解

MySQL数据库约束深入详解

《MySQL数据库约束深入详解》：本文主要介绍MySQL数据库约束,在MySQL数据库中,约束是用来限制进入表中的数据类型的一种技术,通过使用约束,可以确保数据的准确性、完整性和可靠性,需要的朋友... 目录一、数据库约束的概念二、约束类型三、NOT NULL 非空约束四、DEFAULT 默认值约束五、UN
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MySQL 多表连接操作方法(INNER JOIN、LEFT JOIN、RIGHT JOIN、FULL OUTER JOIN)

MySQL 多表连接操作方法(INNER JOIN、LEFT JOIN、RIGHT JOIN、FULL OUTER JOIN)

《MySQL多表连接操作方法(INNERJOIN、LEFTJOIN、RIGHTJOIN、FULLOUTERJOIN)》多表连接是一种将两个或多个表中的数据组合在一起的SQL操作,通过连接,... 目录一、 什么是多表连接？二、 mysql 支持的连接类型三、 多表连接的语法四、实战示例 数据准备五、连接的性
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MySQL中的分组和多表连接详解

MySQL中的分组和多表连接详解

《MySQL中的分组和多表连接详解》：本文主要介绍MySQL中的分组和多表连接的相关操作,本文通过实例代码给大家介绍的非常详细,感兴趣的朋友一起看看吧... 目录mysql中的分组和多表连接一、MySQL的分组（group javascriptby ）二、多表连接（表连接会产生大量的数据垃圾）MySQL中的
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MySQL 中的 JSON 查询案例详解

MySQL 中的 JSON 查询案例详解

《MySQL中的JSON查询案例详解》：本文主要介绍MySQL的JSON查询的相关知识,本文给大家介绍的非常详细,对大家的学习或工作具有一定的参考借鉴价值,需要的朋友参考下吧... 目录mysql 的 jsON 路径格式基本结构路径组件详解特殊语法元素实际示例简单路径复杂路径简写操作符注意MySQL 的 J
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Windows 上如果忘记了 MySQL 密码 重置密码的两种方法

Windows 上如果忘记了 MySQL 密码 重置密码的两种方法

《Windows上如果忘记了MySQL密码重置密码的两种方法》：本文主要介绍Windows上如果忘记了MySQL密码重置密码的两种方法,本文通过两种方法结合实例代码给大家介绍的非常详细,感... 目录方法 1：以跳过权限验证模式启动 mysql 并重置密码方法 2：使用 my.ini 文件的临时配置在 Wi
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MySQL重复数据处理的七种高效方法

MySQL重复数据处理的七种高效方法

《MySQL重复数据处理的七种高效方法》你是不是也曾遇到过这样的烦恼：明明系统测试时一切正常,上线后却频频出现重复数据,大批量导数据时,总有那么几条不听话的记录导致整个事务莫名回滚,今天,我就跟大家分... 目录1. 重复数据插入问题分析1.1 问题本质1.2 常见场景图2. 基础解决方案：使用异常捕获3.
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SQL中redo log 刷⼊磁盘的常见方法

SQL中redo log 刷⼊磁盘的常见方法

《SQL中redolog刷⼊磁盘的常见方法》本文主要介绍了SQL中redolog刷⼊磁盘的常见方法,将redolog刷入磁盘的方法确保了数据的持久性和一致性,下面就来具体介绍一下,感兴趣的可以了解... 目录Redo Log 刷入磁盘的方法Redo Log 刷入磁盘的过程代码示例（伪代码）在数据库系统中，r
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mysql中的group by高级用法

mysql中的group by高级用法

《mysql中的groupby高级用法》MySQL中的GROUPBY是数据聚合分析的核心功能,主要用于将结果集按指定列分组,并结合聚合函数进行统计计算,下面给大家介绍mysql中的groupby用法... 目录一、基本语法与核心功能二、基础用法示例1. 单列分组统计2. 多列组合分组3. 与WHERE结合使
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