mysql 查询锁表的sql mysql查询导致锁表

查询慢的原因：1.数据量大 2.加索引及索引优化，explain查看是否命中索引 3.关联查询时，2张表的编码是否一致，具体见“mysql改变表编码及注意事项”

第一种：

前提条件：找到执行非常慢的sql；

如何找呢：还原客户遇到的问题场景，从控制台找到所执行的sql，一句句的去执行，直到找到执行非常慢的sql

1.查询是否锁表

show OPEN TABLES where In_use > 0;

2.查询进程（如果您有SUPER权限，您可以看到所有线程。否则，您只能看到您自己的线程）

show processlist

3.杀死conmand为waiting的进程id（就是上面命令的id列）

kill id

 

第二种：

1.查看下在锁的事务 

SELECT * FROM INFORMATION_SCHEMA.INNODB_TRX;

2.杀死进程id（就是上面命令的trx_mysql_thread_id列）

kill 线程ID

第三种：

也许你无法查看到所在的info，这个时候你需要重启服务器，如果是分布式的话，就一台台重启吧；

原理是：杀死所有进程，释放所有锁。

MySQL - 锁等待超时与information_schema的三个表：
-- 1.information_schema.innodb_trx–当前运行的所有事务
select * from information_schema.innodb_trx;-- information_schema.innodb_locks–当前出现的锁
select * from information_schema.innodb_locks;-- information_schema.innodb_lock_waits–锁等待的对应关系
select * from information_schema.innodb_lock_waits;
-------------------------------------------------------------------------------------------
//常用MySQL - 锁等待超时与information_schema的三个表：
-- 1.information_schema.innodb_trx–当前运行的所有事务
select * from information_schema.innodb_trx;-- information_schema.innodb_locks–当前出现的锁
select * from information_schema.innodb_locks;-- information_schema.innodb_lock_waits–锁等待的对应关系
select * from information_schema.innodb_lock_waits;
-------------------------------------------------------------------------------------------
//常用
select * from information_schema.innodb_trx where trx_state = 'LOCK WAIT';SELECT a.* FROM information_schema.processlist  a where command <> 'sleep' ORDER BY time desc
select * from information_schema.processlist where time> 60 and user='srapp_stsj';
SELECT
	 concat('kill',' ', id,';')
FROM
	information_schema. PROCESSLIST a
WHERE
	command <> 'sleep'
AND info LIKE 'select%'
AND time > 60
and user = 'srapp_stsj'
ORDER BY
	time DESCEXPLAIN
select * from sr_main where  sys_scbj = '0' and mdjlx = 'ls_jz' and sys_spzt = 2 
and mhzsfz = '330219193210200010' 
----------------------------------------------------------------------------------------------------------------------------------------------
MySQL - 锁等待超时与information_schema的三个表：
-- 1.information_schema.innodb_trx–当前运行的所有事务
select *,trx_mysql_thread_id from information_schema.innodb_trx ;-- information_schema.innodb_locks–当前出现的锁
select * from information_schema.innodb_locks;-- information_schema.innodb_lock_waits–锁等待的对应关系
select * from information_schema.innodb_lock_waits;-------------------------------------------------------------------------------------------
伟哥：命令是用来查看当前运行的所有事务
SELECT
	trx_state,
	trx_started,
	trx_mysql_thread_id,
	trx_query,
	concat(
		'kill ',
		trx_mysql_thread_id,
		';'
	)
FROM
	information_schema.innodb_trx
ORDER BY
	trx_started -- limit 50show processlist  看看有没有锁表
kill id
kill 34116988;kill 50403077; kill 50508905-------------------------------------------------------------------------------------------
//常用
select * from information_schema.innodb_trx where trx_state = 'LOCK WAIT';SELECT a.* FROM information_schema.processlist  a where command <> 'sleep' ORDER BY time desc
select * from information_schema.processlist where time> 60 and user='srapp_stsj';
SELECT
	 concat('kill',' ', id,';')
FROM
	information_schema. PROCESSLIST a
WHERE
	command <> 'sleep'
AND info LIKE 'select%'
AND time > 60
 and user = 'srapp_stsj'
ORDER BY
	time DESC
----------------------------
SELECT
	 concat('kill',' ', id,';')
FROM
	information_schema. PROCESSLIST a
WHERE
	command <> 'sleep'
AND info LIKE 'select%'
AND time > 60
 and user = 'srapp_stsj'
ORDER BY
	time DESC
------------------------------
SELECT
	 *
FROM
	information_schema. PROCESSLIST a
WHERE
	command <> 'sleep'
AND info LIKE 'select%'
AND time > 60
 and user = 'srapp_stsj'
ORDER BY
	time DESCEXPLAIN
select * from sr_main where  sys_scbj = '0' and mdjlx = 'ls_jz' and sys_spzt = 2 
and mhzsfz = '330219193210200010'EXPLAIN
select 1 from sr_main where 1
---------------------------------------
SELECT
	 *
FROM
	information_schema. PROCESSLIST a
WHERE
	command <> 'sleep'
AND info LIKE 'select%'
AND time > 60
 and user = 'srapp_stsj'
ORDER BY
	time DESCSELECT
concat('kill',' ', trx_mysql_thread_id,';')
FROM
information_schema.innodb_trx