查看表描述以及表結構

查看數據庫名

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

查看數據庫中表的列表

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());

獲取表的詳細結構信息

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';

查看創建表的SQL

SHOW CREATE TABLE manager_user;

查看表有哪些索引

SHOW INDEX FROM manager_user;

查看連接數及緩存

查看連接數

SHOW STATUS LIKE 'Threads_connected';
查看所有連接詳情
SHOW FULL PROCESSLIST;
查看連接限制
SHOW VARIABLES LIKE "max_connections";
修改最大連接數
SET GLOBAL max_connections = 1000;
查看等待的連接數（如果啟用了連接隊列）
SHOW STATUS LIKE 'Threads_running';

查看緩存及命中率

查看查詢緩存狀態：
SHOW STATUS LIKE 'Qcache%';
查看慢查詢日志記錄：
SHOW GLOBAL STATUS LIKE 'Slow_queries';
查看表鎖定情況：
SHOW OPEN TABLES WHERE In_use > 0;

性能指標

1、IOPS：(Input/Output operations Per Second，既每秒處理I/O的請求次數)

這個指標根存儲介質的性能是息息相關的，可以把普通機械硬盤替換為SSD固態硬盤是提高MySql處理能力。

2、QPS(Query Per Second，既每秒請求查詢次數)

MySql啟動后查詢請求的總數量：questions = show global status like 'questions';

MySql本次啟動后的運行時間(單位：秒)：uptimes = show global status LIKE 'uptime';

QPS = questions/uptimes

3、TPS(Transcantion Per Second，既每秒事務數)

InnoDB引擎下才會有這個指標數據，TPS涉及到事務的提交與回滾。

commit = show global status like "Com_commit";

rollback = show global status like "Com_rollback";

TPS= (commit+rollback)/seconds(單位時間，單位：秒)