MySQL5.7的新特性

MySQL 5.7版本据说已经在了很大的性能提升以及做得更加安全了，想了解更多MySQL 5.7的新特性可以参考我转载叶金荣老师的MySQL 5.7的新特性说明。这里我简单演示一下MySQL 5.7的安装已经一些新特性的使用，希望大家能一起进去，一起探讨技术。

MySQL 5.7的官方下载地址：http://cdn.mysql.com//Downloads/MySQL-5.7/mysql-5.7.10-linux-glibc2.5-x86_64.tar.gz

下面简单介绍一下安装：

[root@MySQL soft]# tar xf mysql-5.7.-linux-glibc2.-x86_64.tar.gz -C /data/service/
[root@MySQL soft]# cd /data/service/
[root@MySQL service]# mv mysql-5.7.-linux-glibc2.-x86_64/ mysql-5.7.

下面进行数据目录的创建以及授权：

[root@MySQL service]#  mkdir /data/{mysql3306,mysql3306log} -p
[root@MySQL service]# groupadd mysql
[root@MySQL service]# useradd -r -g mysql mysql
[root@MySQL service]# chown -R mysql:mysql mysql-5.7./
[root@MySQL service]# chown -R mysql:mysql /data/mysql3306*

基本操作已经完成，下面进行初始化操作，在MySQL 5.7的初始化操作与MySQL 5.6有点不同了，下面在MySQL 5.7的版本用MySQL 5.6的初始化方式进行操作一下，让大家看下会报什么错：

[root@MySQL mysql-5.7.]# ./bin/mysql_install_db --user=mysql --datadir=/data/mysql3306
-- :: [WARNING] mysql_install_db is deprecated. Please consider switching to mysqld --initialize
-- :: [ERROR]   The bootstrap log isn't empty:
-- :: [ERROR]   --21T03::.633658Z  [Warning] --bootstrap is deprecated. Please consider using --initialize instead
--21T03::.641584Z  [ERROR] Can't read from messagefile '/usr/share/mysql/english/errmsg.sys'
[root@MySQL mysql-5.7.]# 

可以看到mysql_install_db is deprecated，说不赞同使用mysql_install_db，推荐使用的方法是：

Please consider switching to mysqld --initialize ，Please consider using --initialize instead

正确的初始方式如下：./bin/mysqld --initialize --user=mysql --basedir=/data/service/mysql-5.7.10/  --datadir=/data/mysql3306，如果datadir目录有文件，则会报以下错：

[root@MySQL mysql-5.7.]# ./bin/mysqld --initialize --user=mysql --basedir=/data/service/mysql-5.7./  --datadir=/data/mysql3306
--21T05::.355999Z  [Warning] TIMESTAMP with implicit DEFAULT value is deprecated. Please use --explicit_defaults_for_timestamp server option (see documentation for more details).
--21T05::.357796Z  [ERROR] --initialize specified but the data directory has files in it. Aborting.
--21T05::.357814Z  [ERROR] Aborting

所以要把data directory文件删除掉再执行，如果删除目录下的文件还是报同样的错，可以试试把目录删除掉，再创建一个，然后授权：

[root@MySQL mysql-5.7.]# ./bin/mysqld --initialize --user=mysql --basedir=/data/service/mysql-5.7./  --datadir=/data/mysql3306
--21T05::.804937Z  [Warning] TIMESTAMP with implicit DEFAULT value is deprecated. Please use --explicit_defaults_for_timestamp server option (see documentation for more details).
--21T05::.552899Z  [Warning] InnoDB: New log files created, LSN=
--21T05::.816849Z  [Warning] InnoDB: Creating foreign key constraint system tables.
--21T05::.883956Z  [Warning] No existing UUID has been found, so we assume that this is the first time that this server has been started. Generating a new UUID: 660686ae-c002-11e5-843e-00163e0217d7.
--21T05::.886131Z  [Warning] Gtid table is not ready to be used. Table 'mysql.gtid_executed' cannot be opened.
--21T05::.887120Z  [Note] A temporary password is generated for root@localhost: )vyd3aXj8hhC

MySQL 5.7初始化完后会生成一个临时的密码，A temporary password is generated for root@localhost: )vyd3aXj8hhC 如果想初始化表空间，在后面加上 --innodb_data_file_path=ibdata1:1G:autoextend即可。

启动MySQL 5.7，拷贝support-files/my-default.cnf ./

[root@MySQL mysql-5.7.]# cp support-files/my-default.cnf ./my.cnf
[root@MySQL mysql-5.7.]# chown -R mysql:mysql my.cnf 

编辑my.cnf加上基本选项：

[mysqld]
# changes to the binary log between backups.
log_bin

# These are commonly set, remove the # and set as required.
basedir =  /data/service/mysql-5.7.
datadir = /data/mysql3306
port =
server_id =
socket = /tmp/mysqld.sock

编辑启动脚本：

[root@MySQL mysql-5.7.]# cat start_mysql.sh
#!/bin/bash

nohup /data/service/mysql-5.7./bin/mysqld_safe --defaults-file=/data/service/mysql-5.7./my.cnf > /data/service/mysql-5.7./start_stop.log >& &

运行脚本启动 sh start_mysql.sh 。

登录MySQL 5.7，先添加MySQL 5.7的bin路径：

[root@MySQL mysql-5.7.]# cat /etc/profile.d/mysql.sh
export PATH=/data/service/mysql-5.7./bin:$PATH
[root@MySQL mysql-5.7.]# source /etc/profile.d/mysql.sh 

登录时输入的密码是刚刚初始化完的密码：

[root@MySQL mysql-5.7.]# mysql -uroot -p')vyd3aXj8hhC' -S /tmp/mysqld.sock
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is
Server version: 5.7.-log

Copyright (c) , , 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.

mysql> 

第一次登录，是必须要修改密码才能查看show databases;

mysql> show databases;
ERROR 1820 (HY000): You must reset your password using ALTER USER statement before executing this statement.
mysql> 

从上面的信息可以看到，叫我们使用ALTER USER进行修改，下面我们修改一下密码，有关更多MySQL 5.7的用户密码设置可以参考：https://dev.mysql.com/doc/refman/5.7/en/password-expiration-policy.html

mysql> ALTER USER USER() IDENTIFIED BY '';
Query OK, 0 rows affected (0.01 sec)

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
4 rows in set (0.00 sec)

mysql> 

MySQL 5.7的mysql.user表已经没有password这一列了，所以查询用户和密码的方式如下：

mysql> select user,host,authentication_string from mysql.user;
+-----------+-----------+-------------------------------------------+
| user      | host      | authentication_string                     |
+-----------+-----------+-------------------------------------------+
| root      | localhost | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
| mysql.sys | localhost | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE |
+-----------+-----------+-------------------------------------------+
2 rows in set (0.00 sec)

mysql> select password('123456');
+-------------------------------------------+
| password('123456')                        |
+-------------------------------------------+
| *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
+-------------------------------------------+
1 row in set, 1 warning (0.00 sec)

MySQL 5.7支持为表增加计算列

什么叫计算列呢，简单来说就是某一列的值是通过别的列计算得来，例如a列值为1，b列值为2，c列不需要操作手动插入，定义为a + b的结果为c的值，那么c就是计算列，是通过别的列计算得来，下面我们进行例子说明：

在MySQL 5.7之前的版本中，要实现这样的效果要利用触发器来完成，以下是以前的实现过程：

mysql> show create  table tb1\G
*************************** 1. row ***************************
       Table: tb1
Create Table: CREATE TABLE `tb1` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `c1` int(11) DEFAULT NULL,
  `c2` int(11) DEFAULT NULL,
  `c3` int(11) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_bin
1 row in set (0.01 sec)

mysql> 

创建一个插入的触发器：

mysql> create trigger insert_tb1 before insert on tb1 for each row set new.c3=new.c1+new.c2;
Query OK, 0 rows affected (0.01 sec)

我们插入数据：

mysql> insert into tb1(c1,c2) values (1,2);
Query OK, 1 row affected (0.00 sec)

mysql> select * from tb1;
+----+------+------+------+
| id | c1   | c2   | c3   |
+----+------+------+------+
|  1 |    1 |    2 |    3 |
+----+------+------+------+
1 row in set (0.00 sec)

mysql> 

但如果我们更新了c1或者c2的值，c3是不会变动的，所以我们要加一个update的触发器：

mysql> select * from tb1;
+----+------+------+------+
| id | c1   | c2   | c3   |
+----+------+------+------+
|  1 |    1 |    2 |    3 |
+----+------+------+------+
1 row in set (0.00 sec)

mysql>  create trigger update_tb1 before update on tb1 for each row set new.c3=new.c1+new.c2;
Query OK, 0 rows affected (0.01 sec)

mysql> update tb1 set c1 = 3;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> select * from tb1;
+----+------+------+------+
| id | c1   | c2   | c3   |
+----+------+------+------+
|  1 |    3 |    2 |    5 |
+----+------+------+------+
1 row in set (0.00 sec)

mysql> 

可以看到，如果想实现计算列，那么就要借助触发器或者视图来实现，但在生产环境中，是不太建议使用触发器或者视图的。下面用MySQL 5.7来实现就变得很简单了。

MySQL 5.7计算列的实现：

在CREAE TABLE和ALTER TABLE 中都支持增加计算列的方式：

col_name data_type [GENERATED ALWAYS] AS (expression)
      [VIRTUAL | STORED] [UNIQUE [KEY]] [COMMENT comment]
      [NOT NULL | NULL] [[PRIMARY] KEY]

下面我们创建测试表tb2:

mysql> show create table tb2\G
*************************** 1. row ***************************
       Table: tb2
Create Table: CREATE TABLE `tb2` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `c1` int(11) DEFAULT NULL,
  `c2` int(11) DEFAULT NULL,
  `c3` int(11) GENERATED ALWAYS AS ((`c1` + `c2`)) VIRTUAL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1
1 row in set (0.00 sec)

mysql> 

插入数据看效果：

mysql> select * from tb2;
Empty set (0.00 sec)

mysql> insert into tb2(c1,c2) values (1,2);
Query OK, 1 row affected (0.00 sec)

mysql> select * from tb2;
+----+------+------+------+
| id | c1   | c2   | c3   |
+----+------+------+------+
|  1 |    1 |    2 |    3 |
+----+------+------+------+
1 row in set (0.00 sec)

mysql> 

更新数据看效果：

mysql> update tb2 set c1=10;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> select * from tb2;
+----+------+------+------+
| id | c1   | c2   | c3   |
+----+------+------+------+
|  1 |   10 |    2 |   12 |
+----+------+------+------+
1 row in set (0.00 sec)

mysql> 

可以看到相当的方便，MySQL 5.7的很多新特性都给我们带来了便利和惊喜^.^

总结：

     一、MySQL 5.7初始方法相比之前的版本都有所不同，做的相对更为安全了，以前版本初始化完root密码是空的，MySQL 5.7则有一个临时密码。

     二、MySQL 5.7在CREAE TABLE和ALTER TABLE 中都支持增加计算列的方式了，所有可以少用触发器和视图来实现计算列了。

     三、MySQL 5.7无论在性能还是安全性方面都得到了很大的提升，希望小伙伴们一起好好学习MySQL 5.7的一些新特性。

参考资料：

http://dev.mysql.com/doc/refman/5.7/en/binary-installation.html

https://dev.mysql.com/doc/refman/5.7/en/password-expiration-policy.html

http://dev.mysql.com/doc/refman/5.7/en/create-table.html

作者：陆炫志

出处：xuanzhi的博客 http://www.cnblogs.com/xuanzhi201111

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