mysql

MySQL Database Management

Overview

Daily management, backup and recovery, performance tuning, and other operational skills for MySQL/MariaDB databases.

Connection Management

# 本地连接
mysql -u root -p

# 远程连接
mysql -h hostname -P 3306 -u user -p database

# 执行 SQL 文件
mysql -u user -p database < script.sql

Execute a Single Command

mysql -u user -p -e "SHOW DATABASES;"

## 用户与权限

```sql
-- 查看用户
SELECT user, host FROM mysql.user;

-- 创建用户
CREATE USER 'username'@'%' IDENTIFIED BY 'password';

-- 授权
GRANT ALL PRIVILEGES ON database.* TO 'username'@'%';
GRANT SELECT, INSERT ON database.table TO 'username'@'%';

-- 刷新权限
FLUSH PRIVILEGES;

-- 查看权限
SHOW GRANTS FOR 'username'@'%';

Database Operations

-- 数据库管理
SHOW DATABASES;
CREATE DATABASE dbname CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;
DROP DATABASE dbname;
USE dbname;

-- 表管理
SHOW TABLES;
DESCRIBE tablename;
SHOW CREATE TABLE tablename;

Backup and Recovery

mysqldump Backup

# 备份单个数据库
mysqldump -u root -p database > backup.sql

# 备份所有数据库
mysqldump -u root -p --all-databases > all_backup.sql

# 备份表结构
mysqldump -u root -p --no-data database > schema.sql

# 压缩备份
mysqldump -u root -p database | gzip > backup.sql.gz

Recovery

# 恢复数据库
mysql -u root -p database < backup.sql

# 从压缩文件恢复
gunzip < backup.sql.gz | mysql -u root -p database

Performance Monitoring

-- 查看进程
SHOW PROCESSLIST;
SHOW FULL PROCESSLIST;

-- 查看状态
SHOW STATUS;
SHOW GLOBAL STATUS LIKE 'Threads%';
SHOW GLOBAL STATUS LIKE 'Connections';

-- 查看变量
SHOW VARIABLES LIKE 'max_connections';
SHOW VARIABLES LIKE '%buffer%';

-- 慢查询
SHOW VARIABLES LIKE 'slow_query%';
SHOW GLOBAL STATUS LIKE 'Slow_queries';

Common Scenarios

Scenario 1: Troubleshooting Slow Queries

-- 开启慢查询日志
SET GLOBAL slow_query_log = 'ON';
SET GLOBAL long_query_time = 1;

-- 查看慢查询日志位置
SHOW VARIABLES LIKE 'slow_query_log_file';

-- 分析执行计划
EXPLAIN SELECT * FROM table WHERE condition;
EXPLAIN ANALYZE SELECT * FROM table WHERE condition;

Scenario 2: Troubleshooting Lock Issues

-- 查看锁等待
SHOW ENGINE INNODB STATUS\G

-- 查看当前锁
SELECT * FROM information_schema.INNODB_LOCKS;
SELECT * FROM information_schema.INNODB_LOCK_WAITS;

-- 查看事务
SELECT * FROM information_schema.INNODB_TRX;

Scenario 3: Primary-Replica Replication Status

-- 主库状态
SHOW MASTER STATUS;

-- 从库状态
SHOW SLAVE STATUS\G

-- 关键指标
-- Slave_IO_Running: Yes
-- Slave_SQL_Running: Yes
-- Seconds_Behind_Master: 0

Troubleshooting

Issue	Troubleshooting Method
Too Many Connections	SHOW PROCESSLIST, check max_connections
Slow Queries	EXPLAIN, check indexes
Lock Waits	SHOW ENGINE INNODB STATUS
Replication Lag	SHOW SLAVE STATUS, check network and load
Disk Full	Check binlog, clean up old logs