查看表描述以及表结构

查看数据库名

SHOW DATABASES;
SELECT DATABASE();
SELECT DATABASE() AS current_database;

查看数据库中表的列表

SHOW TABLES;
SELECT TABLE_NAME, TABLE_COMMENT FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_SCHEMA ='your_database_name';
SELECT TABLE_NAME, TABLE_COMMENT FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_SCHEMA = (SELECT DATABASE());
SELECT TABLE_NAME, TABLE_COMMENT FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_SCHEMA IN (SELECT DATABASE());

获取表的详细结构信息

DESC manager_user;
DESCRIBE manager_user;
SHOW FIELDS FROM manager_user;
SHOW COLUMNS FROM manager_user;
SHOW FULL COLUMNS FROM manager_user;
SELECT * FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_SCHEMA = 'your_database_name' AND TABLE_NAME = 'your_table_name';
SELECT * FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_SCHEMA = (SELECT DATABASE()) AND TABLE_NAME = 'manager_user';

查看创建表的SQL

SHOW CREATE TABLE manager_user;

查看表有哪些索引

SHOW INDEX FROM manager_user;

查看连接数及缓存

查看连接数

SHOW STATUS LIKE 'Threads_connected';
查看所有连接详情
SHOW FULL PROCESSLIST;
查看连接限制
SHOW VARIABLES LIKE "max_connections";
修改最大连接数
SET GLOBAL max_connections = 1000;
查看等待的连接数（如果启用了连接队列）
SHOW STATUS LIKE 'Threads_running';

查看缓存及命中率

查看查询缓存状态：
SHOW STATUS LIKE 'Qcache%';
查看慢查询日志记录：
SHOW GLOBAL STATUS LIKE 'Slow_queries';
查看表锁定情况：
SHOW OPEN TABLES WHERE In_use > 0;

性能指标

1、IOPS：(Input/Output operations Per Second，既每秒处理I/O的请求次数)

这个指标根存储介质的性能是息息相关的，可以把普通机械硬盘替换为SSD固态硬盘是提高MySql处理能力。

2、QPS(Query Per Second，既每秒请求查询次数)

MySql启动后查询请求的总数量：questions = show global status like 'questions';

MySql本次启动后的运行时间(单位：秒)：uptimes = show global status LIKE 'uptime';

QPS = questions/uptimes

3、TPS(Transcantion Per Second，既每秒事务数)

InnoDB引擎下才会有这个指标数据，TPS涉及到事务的提交与回滚。

commit = show global status like "Com_commit";

rollback = show global status like "Com_rollback";

TPS= (commit+rollback)/seconds(单位时间，单位：秒)