1，into outfile 生成sql：一般都是生成文本或者其他形式的文件，现在需要生成sql形式的文件。
select concat('insert into tab_name(col1,col2,col3) values(',col1,',','\'',col2,'\'',',','\'',col3,'\'',')') into outfile '/tmp/tt.txt' from tt;
出来tt.txt的结果为：
insert into tab_name(id,name,age) values(1,'aaa','23'); insert into tab_name(id,name,age) values(2,'aaa','23'); insert into tab_name(id,name,age) values(3,'aaa','23'); insert into tab_name(id,name,age) values(4,'aaa','23'); insert into tab_name(id,name,age) values(6,'aaa','23');
2，MySQL中like语句及相关优化器tips： 利用INNODB特性，来优化like '%%'的方法。
3，Mysqldump输出方式和进度报告： 用这个mysqldump可以直接在备份的时候打印出进度。注意，需要有可执行权限和64位系统。
./mysqldump -uroot -p -h192.168.1.11 --default-character-set=utf8 dbname tablename --result-file=table.sql --progress-reportEnter current_table: dbname.tablename Stage: 10%
4，在show processlist显示的状态里面，update表示正在insert ，updating表示正在delete，Updating才是表示正在update。
5，Innodb表，当表里面有100行记录，有自增ID。清除表里的数据之后，重启数据库。发现表的自增ID重新计算，从0开始。MyISAM表不会。
root@localhost : test 05:12:51>show create table tte\G; *************************** 1. row *************************** Table: tte Create Table: CREATE TABLE `tte` ( `id` int(11) NOT NULL AUTO_INCREMENT, `name` varchar(10) DEFAULT NULL, `age` int(11) DEFAULT NULL, `address` varchar(100) DEFAULT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8 ROW_FORMAT=REDUNDANT 1 row in set (0.00 sec) ERROR: No query specified root@localhost : test 05:13:58>insert into tte(name,age,address) values('a',11,'hz'),('b',22,'gz'),('c',33,'bj'); Query OK, 3 rows affected (0.00 sec) Records: 3 Duplicates: 0 Warnings: 0 root@localhost : test 05:14:39>select * from tte; +----+------+------+---------+ | id | name | age | address | +----+------+------+---------+ | 1 | a | 11 | hz | | 2 | b | 22 | gz | | 3 | c | 33 | bj | +----+------+------+---------+ 3 rows in set (0.00 sec) root@localhost : test 05:14:44>show create table tte\G; *************************** 1. row *************************** Table: tte Create Table: CREATE TABLE `tte` ( `id` int(11) NOT NULL AUTO_INCREMENT, `name` varchar(10) DEFAULT NULL, `age` int(11) DEFAULT NULL, `address` varchar(100) DEFAULT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8 ROW_FORMAT=REDUNDANT 1 row in set (0.00 sec) ERROR: No query specified root@localhost : test 05:14:46>delete from tte; Query OK, 3 rows affected (0.00 sec) root@localhost : test 05:14:59>show create table tte\G; *************************** 1. row *************************** Table: tte Create Table: CREATE TABLE `tte` ( `id` int(11) NOT NULL AUTO_INCREMENT, `name` varchar(10) DEFAULT NULL, `age` int(11) DEFAULT NULL, `address` varchar(100) DEFAULT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8 ROW_FORMAT=REDUNDANT 1 row in set (0.00 sec) ERROR: No query specified root@localhost : test 05:15:04>\q Bye zhoujy@zhoujy:~$ sudo /etc/init.d/mysql restart [sudo] password for zhoujy: Rather than invoking init scripts through /etc/init.d, use the service(8) utility, e.g. service mysql restart Since the script you are attempting to invoke has been converted to an Upstart job, you may also use the stop(8) and then start(8) utilities, e.g. stop mysql ; start mysql. The restart(8) utility is also available. mysql stop/waiting mysql start/running, process 5285 zhoujy@zhoujy:~$ mysql test Reading table information for completion of table and column names You can turn off this feature to get a quicker startup with -A Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 3 Server version: 5.1.67-0ubuntu0.11.10.1-log (Ubuntu) Copyright (c) 2000, 2012, Oracle and/or its affiliates. All rights reserved. Oracle is a registered trademark of Oracle Corporation and/or its affiliates. Other names may be trademarks of their respective owners. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement. root@localhost : test 05:15:22>show create table tte\G; *************************** 1. row *************************** Table: tte Create Table: CREATE TABLE `tte` ( `id` int(11) NOT NULL AUTO_INCREMENT, `name` varchar(10) DEFAULT NULL, `age` int(11) DEFAULT NULL, `address` varchar(100) DEFAULT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8 ROW_FORMAT=REDUNDANT 1 row in set (0.00 sec) ERROR: No query specified root@localhost : test 05:15:24>insert into tte(name,age,address) values('a',11,'hz'),('b',22,'gz'),('c',33,'bj'); Query OK, 3 rows affected (0.00 sec) Records: 3 Duplicates: 0 Warnings: 0 root@localhost : test 05:15:37>select * from tte; +----+------+------+---------+ | id | name | age | address | +----+------+------+---------+ | 1 | a | 11 | hz | | 2 | b | 22 | gz | | 3 | c | 33 | bj | +----+------+------+---------+ 3 rows in set (0.00 sec)
6，MySQL中pager的使用：Pager的使用
7，MySQL之 index_merge 的弃用：当执行计划出现索引合并时，可以修改optimizer_switch的一个状态，弃用index_merge索引，要慎用
set optimizer_switch = 'index_merge_union=off,index_merge_intersection=off,index_merge_sort_union=off';
root@localhost : test 02:09:32>explain select * From idx_mer where name='e' and name1 = 'ee'\G; *************************** 1. row *************************** id: 1 select_type: SIMPLE table: idx_mer type: index_merge possible_keys: idx_name,idx_name1 key: idx_name1,idx_name key_len: 33,33 ref: NULL rows: 1 Extra: Using intersect(idx_name1,idx_name); Using where 1 row in set (0.00 sec) root@localhost : test 02:09:36>set session optimizer_switch='index_merge_intersection=off'; Query OK, 0 rows affected (0.00 sec) root@localhost : test 02:10:12>explain select * From idx_mer where name='e' and name1 = 'ee'\G; *************************** 1. row *************************** id: 1 select_type: SIMPLE table: idx_mer type: ref possible_keys: idx_name,idx_name1 key: idx_name1 key_len: 33 ref: const rows: 2 Extra: Using where 1 row in set (0.00 sec)
8，MySQL提示符设置：prompt
[client] #在client组下面设置 prompt = \\u@\\h : \\d \\r:\\m:\\s> #屏幕输出打印到指定位置 tee = /home/mysql/query.log 效果： root@localhost : test 09:54:37>
9，MySQL隔离级别 read committed下的注意事项：在read committed/uncommitted 隔离级别下面，binlog 的 statement模式不被支持。
mysql> select @@global.tx_isolation,@@global.binlog_format; +-----------------------+------------------------+ | @@global.tx_isolation | @@global.binlog_format | +-----------------------+------------------------+ | READ-COMMITTED | ROW | +-----------------------+------------------------+ 1 row in set (0.00 sec) mysql> select @@session.tx_isolation,@@session.binlog_format; +------------------------+-------------------------+ | @@session.tx_isolation | @@session.binlog_format | +------------------------+-------------------------+ | READ-COMMITTED | ROW | +------------------------+-------------------------+ 1 row in set (0.00 sec) mysql> set session binlog_format='statement'; Query OK, 0 rows affected (0.00 sec) mysql> insert into test values(1,'test',1); #在read committed/uncommitted 隔离级别下面，binlog 的 statement模式不被支持。 ERROR 1665 (HY000): Cannot execute statement: impossible to write to binary log since BINLOG_FORMAT = STATEMENT and at least one table uses a storage engine limited to row-based logging. InnoDB is limited to row-logging when transaction isolation level is READ COMMITTED or READ UNCOMMITTED. mysql> select @@session.tx_isolation,@@session.binlog_format; +------------------------+-------------------------+ | @@session.tx_isolation | @@session.binlog_format | +------------------------+-------------------------+ | READ-COMMITTED | STATEMENT | +------------------------+-------------------------+ 1 row in set (0.00 sec) mysql> set session transaction isolation level repeatable read,binlog_format = statement; Query OK, 0 rows affected (0.00 sec) mysql> select @@session.tx_isolation,@@session.binlog_format; +------------------------+-------------------------+ | @@session.tx_isolation | @@session.binlog_format | +------------------------+-------------------------+ | REPEATABLE-READ | STATEMENT | +------------------------+-------------------------+ 1 row in set (0.00 sec) mysql> insert into test values(1,'test',1); Query OK, 1 row affected (0.00 sec)
10，innodb表加索引的限制：索引大小需要小于767个字节才能建立成功，767<size<3072：会报warnging，能建立成功但是会被截断，size>3072：会直接报错，不会建立索引。size：长度*字符集大小，如：varchar(10) utf8 则是10*3=30 bytes。
root@localhost : test 03:33:33>show create table tb\G; *************************** 1. row *************************** Table: tb Create Table: CREATE TABLE `tb` ( `a` varchar(256) DEFAULT NULL, `b` varchar(2556) DEFAULT NULL, `c` varchar(256) DEFAULT NULL, `d` varchar(256) DEFAULT NULL, `e` varchar(256) DEFAULT NULL ) ENGINE=InnoDB DEFAULT CHARSET=utf8 1 row in set (0.00 sec) root@localhost : test 03:33:43>alter table tb add index idx_all(a,b); Query OK, 0 rows affected, 4 warnings (0.08 sec) Records: 0 Duplicates: 0 Warnings: 0 root@localhost : test 03:34:05>show warnings; +---------+------+---------------------------------------------------------+ | Level | Code | Message | +---------+------+---------------------------------------------------------+ | Warning | 1071 | Specified key was too long; max key length is 767 bytes | | Warning | 1071 | Specified key was too long; max key length is 767 bytes | | Warning | 1071 | Specified key was too long; max key length is 767 bytes | | Warning | 1071 | Specified key was too long; max key length is 767 bytes | +---------+------+---------------------------------------------------------+ 4 rows in set (0.00 sec) root@localhost : test 03:53:40>alter table tb add index idx_all_5(a,b,c,d,e); ERROR 1071 (42000): Specified key was too long; max key length is 3072 bytes root@localhost : test 03:54:22>show create table tb\G; *************************** 1. row *************************** Table: tb Create Table: CREATE TABLE `tb` ( `a` varchar(256) DEFAULT NULL, `b` varchar(2556) DEFAULT NULL, `c` varchar(256) DEFAULT NULL, `d` varchar(256) DEFAULT NULL, `e` varchar(256) DEFAULT NULL, KEY `idx_all` (`a`(255),`b`(255)) ) ENGINE=InnoDB DEFAULT CHARSET=utf8 1 row in set (0.00 sec)
11，在show processlist显示的状态里面：update表示正在insert ，updating表示正在delete，Updating才是表示正在update。
+-----+------+-----------+------+---------+------+----------------+----------------+ | Id | User | Host | db | Command | Time | State | Info | +-----+------+-----------+------+---------+------+----------------+----------------+ | 322 | root | localhost | test | Query | 1 | updating | delete from ...| | 322 | root | localhost | test | Query | 18 | Updating | update ...| | 322 | root | localhost | test | Query | 49 | update | insert into ...| +-----+------+-----------+------+---------+------+----------------+----------------+
12，清除Slave信息：在5.5之后新增了一个命令：reset slave all，可以清除Slave的所有信息。
mysql> show slave status\G; *************************** 1. row *************************** Slave_IO_State: Master_Host: 192.168.200.25 Master_User: rep Master_Port: 3306 Connect_Retry: 60 Master_Log_File: Read_Master_Log_Pos: 4 Relay_Log_File: mysqld-relay-bin.000001 Relay_Log_Pos: 4 Relay_Master_Log_File: Slave_IO_Running: No Slave_SQL_Running: No Replicate_Do_DB: Replicate_Ignore_DB: Replicate_Do_Table: Replicate_Ignore_Table: Replicate_Wild_Do_Table: Replicate_Wild_Ignore_Table: Last_Errno: 0 Last_Error: Skip_Counter: 0 Exec_Master_Log_Pos: 0 Relay_Log_Space: 126 Until_Condition: None Until_Log_File: Until_Log_Pos: 0 Master_SSL_Allowed: No Master_SSL_CA_File: Master_SSL_CA_Path: Master_SSL_Cert: Master_SSL_Cipher: Master_SSL_Key: Seconds_Behind_Master: NULL Master_SSL_Verify_Server_Cert: No Last_IO_Errno: 0 Last_IO_Error: Last_SQL_Errno: 0 Last_SQL_Error: Replicate_Ignore_Server_Ids: Master_Server_Id: 0 1 row in set (0.00 sec) ERROR: No query specified mysql> reset slave all; Query OK, 0 rows affected (0.00 sec) mysql> show slave status\G; Empty set (0.00 sec)
13，字段类型timestamp在5.6之前，一个表不能定义2个以上的包含（1，default current_timestamp；2，on update current_timestamp）的表定义，否则建表出错。原因见：这里
5.6 之前版本： #不能定义2个列包含 default current_timestamp 和 on update current_timestamp 属性的字段： root@localhost : test 09:29:27>CREATE TABLE `tran1` ( -> `id` int(11) NOT NULL DEFAULT '0', -> `name` varchar(10) DEFAULT NULL, -> `ctime` timestamp default current_timestamp, -> `mtime` timestamp on update current_timestamp, -> PRIMARY KEY (`id`) -> ) ENGINE=InnoDB DEFAULT CHARSET=utf8; ERROR 1293 (HY000): Incorrect table definition; there can be only one TIMESTAMP column with CURRENT_TIMESTAMP in DEFAULT or ON UPDATE clause #能定义同一个列包含 default current_timestamp 和 on update current_timestamp 属性的字段： root@localhost : test 09:29:47>CREATE TABLE `tran1` ( -> `id` int(11) NOT NULL DEFAULT '0', -> `name` varchar(10) DEFAULT NULL, -> `ctime` timestamp default current_timestamp on update current_timestamp, -> `mtime` timestamp, -> PRIMARY KEY (`id`) -> ) ENGINE=InnoDB DEFAULT CHARSET=utf8; Query OK, 0 rows affected (0.27 sec) 5.6版本之后： #没有这个限制： root@192.168.220.200 : test 09:30:03>CREATE TABLE `tran1` ( -> `id` int(11) NOT NULL DEFAULT '0', -> `name` varchar(10) DEFAULT NULL, -> `ctime` timestamp default current_timestamp, -> `mtime` timestamp on update current_timestamp, -> PRIMARY KEY (`id`) -> ) ENGINE=InnoDB DEFAULT CHARSET=utf8; Query OK, 0 rows affected (0.20 sec)
14，mysql -e "command" 生成结果导入指定文件时，若要同时显示语句本身，-v; 若要增加查询结果行数，加-vv; 若要增加执行时间, 加-vvv。
mysql -e "select user,host from mysql.user" -v/-vv/-vvv > 1.txt
15，myisamchk使用注意事项：当一张MYISAM表坏了，索引文件大于sort_buffer_size，要是用myisamchk去修复，会报错，需要手动指定--sort_buffer_size。大小最好设置大于MYI文件的大小。
root@zjy:/data/mysql2/mstem# myisamchk -r -q edail_log.MYI - recovering (with sort) MyISAM-table ' edail_log.MYI' Data records: 0 - Fixing index 1 - Fixing index 2 myisamchk: error: myisam_sort_buffer_size is too small MyISAM-table ' edail_log.MYI' is not fixed because of errors Try fixing it by using the --safe-recover (-o), the --force (-f) option or by not using the --quick (-q) flag root@zjy:/data/mysql2/mstem# myisamchk -r -q --sort_buffer_size=2024M edail_log.MYI - check record delete-chain - recovering (with sort) MyISAM-table ' edail_log.MYI' Data records: 0 - Fixing index 1 - Fixing index 2 - Fixing index 3 Data records: 68464254
16，字符集：utf8mb4：mysql 5.5.3之后出来的字符集，占用1~4个字节，最大占用的字节数为4。目前这个字段主要应用在（Emoji 表情需要4个字节）让Mysql支持Emoji表情 ，utf8mb4兼容utf8（1~3字节），且比utf8能表示更多的字符。什么时候需要才用utf8mb4，否则只是浪费空间（比如utf8占用3个字节，10个汉字占用30个字节。这时候改成utf8mb4也只有30个，物理上占用的空间一样，但是在申请内存的时候，utf8mb4会多于utf8 1个字节）。的时候需要注意：innodb_purge_threads 和 innodb_force_recovery一起设置的时候需要注意：innodb_purge_threads=1时，innodb_force_recovery不能大于1（可以等于1）；当innodb_purge_threads=0时，innodb_force_recovery没有限制。
18，数据库中的加锁协议，分为乐观/悲观两类：乐观加锁，操作记录时不主动加锁，由后续冲突者负责加锁；悲观加锁，操作记录时主动加锁。乐观加锁适用于并发冲突较小时，减少了加锁开销；而悲观加锁适用于并发冲突较大时，简化操作流程。以InnoDB为例，Update采用了悲观加锁协议，Insert则采用了乐观加锁。来自这里
19，Engine=innodb，当table.frm文件丢失时，drop database会出现两种情况： 1）version=5.1,报ERROR 1010 (HY000): Error dropping database (can't rmdir './D1', errno: 39) ；2）version=5.5,正常执行。根源在innobase_drop_database函数的调用顺序的不同。而engine=MyISAM 时，5.1,5.5都报39错误。
20，为什么正则表达式中/d比[0-9]效率差？ /d匹配的是Unicode，所以相当于要筛选各种语言里的数字字符，而[0-9]只匹配这是个数字。
21，5.6之前add foreign key 还是不能使用fast-index-creation. 5.6之后支持，但需要在执行加外键之前先 set foreign_key_checks=0。
22，STATEMENT下5.1到5.5复制的注意事项：5.1 无符号的整数类型，如果相减得到负数，mysql会自动转化为最大的正数；5.5直接报错。
5.1： root@localhost : test 10:24:30>select cast(0 as unsigned)-1; +-----------------------+ | cast(0 as unsigned)-1 | +-----------------------+ | 18446744073709551615 | +-----------------------+ 1 row in set (0.00 sec) 5.5： zjy@192.168.200.233 : (none) 10:25:04>select cast(0 as unsigned)-1; ERROR 1690 (22003): BIGINT UNSIGNED value is out of range in '(cast(0 as unsigned) - 1)'