show VARIABLES like "max_connections";  //最大连接数

show global status like 'Threads_connected'; //当前连接数

show global status like 'Threads_running'; //正在处理的连接数

show global status like 'Thread%'; //查看进行情况

innodb引擎查看死锁语句

select b.trx_mysql_thread_id AS '被阻塞线程',

b.trx_query AS '被阻塞SQL',

c.trx_mysql_thread_id AS '阻塞线程',

(UNIX_TIMESTAMP()-UNIX_TIMESTAMP(c.trx_started)) AS '阻塞时间'

from information_schema.INNODB_LOCK_WAITS a

join information_schema.INNODB_TRX b on a.requesting_trx_id =b.trx_id

join information_schema.INNODB_TRX c on a.blocking_trx_id=c.trx_id

where (UNIX_TIMESTAMP()-UNIX_TIMESTAMP(c.trx_started))>60;

-- 打开sql执行记录功能

set global log_output='TABLE';                             -- 输出到表

set global log=ON;                                                -- 打开所有命令执行记录功能general_log, 所有语句: 成功和未成功的.

set global log_slow_queries=ON;                        -- 打开慢查询sql记录slow_log, 执行成功的: 慢查询语句和未使用索引的语句

set global long_query_time=0.1;                          -- 慢查询时间限制(秒)

set global log_queries_not_using_indexes=ON;  -- 记录未使用索引的sql语句

-- 查询sql执行记录

select * from mysql.slow_log order by 1;           -- 执行成功的：慢查询语句,和未使用索引的语句

select * from mysql.general_log order by 1;      -- 所有语句：  成功和未成功的.

-- 关闭sql执行记录

set global log=OFF;

set global log_slow_queries=OFF;