一、关于锁的三张表（MEMORY引擎）
## 当前运行的所有事务
mysql> select * from information_schema.innodb_trx\G;
*************************** 1. row ***************************
trx_id: 613963
trx_state: LOCK WAIT #事务状态
trx_started: 2019-02-22 10:48:48
trx_requested_lock_id: 613963:460:3:4
trx_wait_started: 2019-02-22 11:08:41
trx_weight: 2
trx_mysql_thread_id: 140
trx_query: update tx1 set c1=‘heyfffff‘,c2=‘heyffffff‘ where id =3
trx_operation_state: starting index read
trx_tables_in_use: 1
trx_tables_locked: 1
trx_lock_structs: 2
trx_lock_memory_bytes: 1136
trx_rows_locked: 7 #事务锁住的行数
trx_rows_modified: 0
trx_concurrency_tickets: 0 #事务并发票数
trx_isolation_level: REPEATABLE READ
trx_unique_checks: 1
trx_foreign_key_checks: 1
trx_last_foreign_key_error: NULL
trx_adaptive_hash_latched: 0
trx_adaptive_hash_timeout: 0
trx_is_read_only: 0
trx_autocommit_non_locking: 0
*************************** 2. row ***************************
trx_id: 613962
trx_state: RUNNING
trx_started: 2019-02-22 10:46:29
trx_requested_lock_id: NULL
trx_wait_started: NULL
trx_weight: 3
trx_mysql_thread_id: 138
trx_query: select * from information_schema.innodb_trx
trx_operation_state: NULL
trx_tables_in_use: 0
trx_tables_locked: 1
trx_lock_structs: 2
trx_lock_memory_bytes: 1136
trx_rows_locked: 1
trx_rows_modified: 1
trx_concurrency_tickets: 0
trx_isolation_level: REPEATABLE READ
trx_unique_checks: 1
trx_foreign_key_checks: 1
trx_last_foreign_key_error: NULL
trx_adaptive_hash_latched: 0
trx_adaptive_hash_timeout: 0
trx_is_read_only: 0
trx_autocommit_non_locking: 0
2 rows in set (0.00 sec)
## 当前出现的锁
mysql> select * from information_schema.innodb_locks\G;
*************************** 1. row ***************************
lock_id: 613963:460:3:4
lock_trx_id: 613963
lock_mode: X
lock_type: RECORD
lock_table: `test`.`tx1`
lock_index: PRIMARY
lock_space: 460
lock_page: 3
lock_rec: 4
lock_data: 3
*************************** 2. row ***************************
lock_id: 613962:460:3:4
lock_trx_id: 613962
lock_mode: X
lock_type: RECORD
lock_table: `test`.`tx1`
lock_index: PRIMARY
lock_space: 460
lock_page: 3
lock_rec: 4
lock_data: 3
2 rows in set, 1 warning (0.00 sec)
## 锁等待的对应关系
mysql> select * from information_schema.innodb_lock_waits\G;
*************************** 1. row ***************************
requesting_trx_id: 613963
requested_lock_id: 613963:460:3:4 #请求锁的锁ID
blocking_trx_id: 613962 #当前拥有锁的事务ID
blocking_lock_id: 613962:460:3:4
1 row in set, 1 warning (0.00 sec)
二、查看锁的情况
mysql> show status like ‘innodb_row_lock_%‘;
+-------------------------------+--------+
| Variable_name | Value |
+-------------------------------+--------+
| Innodb_row_lock_current_waits | 1 |
| Innodb_row_lock_time | 479764 |
| Innodb_row_lock_time_avg | 39980 |
| Innodb_row_lock_time_max | 51021 |
| Innodb_row_lock_waits | 12 |
+-------------------------------+--------+
5 rows in set (0.00 sec)
解释如下：
Innodb_row_lock_current_waits : 当前等待锁的数量
Innodb_row_lock_time : 系统启动到现在，锁定的总时间长度
Innodb_row_lock_time_avg : 每次平均锁定的时间
Innodb_row_lock_time_max : 最长一次锁定时间
Innodb_row_lock_waits : 系统启动到现在总共锁定的次数
# 查询是否锁表
mysql> show OPEN TABLES where In_use > 0;
+----------+-------+--------+-------------+
| Database | Table | In_use | Name_locked |
+----------+-------+--------+-------------+
| test | tx1 | 1 | 0 |
+----------+-------+--------+-------------+
1 row in set (0.00 sec)
三、杀死进程
# 1.查询进程
mysql> show processlist\G # \G 结构旋转90度变成纵向
*************************** 1. row ***************************
Id: 138
User: root
Host: localhost:55106
db: test
Command: Query
Time: 0
State: starting
Info: show processlist
*************************** 2. row ***************************
Id: 140
User: root
Host: localhost:56158
db: test
Command: Sleep
Time: 145
State:
Info: NULL
2 rows in set (0.00 sec)
2 rows in set (0.00 sec)
# 2.杀死对应进程ID
mysql> kill 140;
Query OK, 0 rows affected (0.00 sec)
mysql> show processlist\G
*************************** 1. row ***************************
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Id: 138
User: root
Host: localhost:55106
db: test
Command: Query
Time: 0
State: starting
Info: show processlist
1 row in set (0.00 sec)
四、SQL分析
描述MySQL如何执行查询操作、以及MySQL成功返回结果集需要执行的行数。
0. 1.EXPLAIN tbl_name 或 EXPLAIN [EXTENDED] SELECT select_options
2.
五、数据库的一些默认设置
# 查看数据库默认存储引擎
mysql> show engines;
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| Engine | Support | Comment | Transactions | XA | Savepoints |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| InnoDB | DEFAULT | Supports transactions, row-level locking, and foreign keys | YES | YES | YES |
| MRG_MYISAM | YES | Collection of identical MyISAM tables | NO | NO | NO |
| MEMORY | YES | Hash based, stored in memory, useful for temporary tables | NO | NO | NO |
| BLACKHOLE | YES | /dev/null storage engine (anything you write to it disappears) | NO | NO | NO |
| MyISAM | YES | MyISAM storage engine | NO | NO | NO |
| CSV | YES | CSV storage engine | NO | NO | NO |
| ARCHIVE | YES | Archive storage engine | NO | NO | NO |
| PERFORMANCE_SCHEMA | YES | Performance Schema | NO | NO | NO |
| FEDERATED | NO | Federated MySQL storage engine | NULL | NULL | NULL |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
9 rows in set (0.00 sec)
# 查看当前数据库默认隔离级别
mysql> select @@global.tx_isolation;
+-----------------------+
| @@global.tx_isolation |
+-----------------------+
| REPEATABLE-READ |
+-----------------------+
1 row in set, 1 warning (0.00 sec)
# 默认自动提交事务
mysql> show global variables like ‘autocommit‘;
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| autocommit | ON |
+---------------+-------+
1 row in set (0.00 sec)
mysql> select @@global.autocommit;
+---------------------+
| @@global.autocommit |
+---------------------+
| 1 |
+---------------------+
1 row in set (0.00 sec)
原文地址：https://www.cnblogs.com/qwangxiao/p/10417401.html