MySQL 安装与配置 |

记录 ubuntu18.04 安装并配置 MySQL

安装

$ sudo apt install mysql-server

配置

使用命令出现如下错误，原因及解决方法

$ mysql -ui root -p
ERROR 1698 (28000): Access denied for user 'root'@'localhost'

$ sudo mysql -u root # I had to use "sudo" since is new installation
mysql> USE mysql;
mysql> SELECT User, Host, plugin FROM mysql.user;
+------------------+-----------+-----------------------+
| User             | Host      | plugin                |
+------------------+-----------+-----------------------+
| root             | localhost | auth_socket           |
| mysql.session    | localhost | mysql_native_password |
| mysql.sys        | localhost | mysql_native_password |
| debian-sys-maint | localhost | mysql_native_password |
+------------------+-----------+-----------------------+
4 rows in set (0.00 sec)

mysql> CREATE USER 'sql-test'@'localhost' IDENTIFIED BY '';
Query OK, 0 rows affected (0.00 sec)

mysql> GRANT ALL PRIVILEGES ON *.* TO 'sql-test'@'localhost';
ERROR 1133 (42000): Can't find any matching row in the user table
mysql> GRANT ALL PRIVILEGES ON *.* TO 'sql-test'@'localhost';
Query OK, 0 rows affected (0.00 sec)

mysql> UPDATE user SET plugin='auth_socket' WHERE User='sql-test';
mysql> FLUSH PRIVILEGES;

mysql> SELECT User, Host, plugin FROM mysql.user;
+------------------+-----------+-----------------------+
| User             | Host      | plugin                |
+------------------+-----------+-----------------------+
| root             | localhost | auth_socket           |
| mysql.session    | localhost | mysql_native_password |
| mysql.sys        | localhost | mysql_native_password |
| debian-sys-maint | localhost | mysql_native_password |
| sql-test         | localhost | auth_socket           |
+------------------+-----------+-----------------------+
5 rows in set (0.00 sec)

mysql> UPDATE user SET plugin='mysql_native_password' WHERE User='sql-test';
mysql> FLUSH PRIVILEGES;
mysql> exit;

$ sudo service mysql restart
$ mysql -u sql-test
mysql>

其他命令：

检查MySQL服务器占用端口 netstat -nlt|grep 3306
检查MySQL服务器系统进程 ps -aux|grep mysql
查看数据库的字符集编码 show variables like '%char%';
重启 service mysqld restart

删除用户

存在 root@localhost 和 root@127.0.0.1

mysql> drop user root@127.0.0.1;

修复 root 登录权限

mysql -u root -p 登录失败，必须增加 sudo 才可以正常登录，修复如下

$ sudo service mysql stop
$ sudo mkdir -p /var/run/mysqld
$ sudo chown mysql /var/run/mysqld
$ sudo mysqld_safe --skip-grant-tables &
$ sudo mysqld_safe --skip-grant-tables --skip-syslog --skip-networking
$ mysql -u root
mysql> UPDATE mysql.user SET authentication_string=PASSWORD('123456') WHERE User='root';
mysql> FLUSH PRIVILEGES;
mysql> quit;

$ sudo service mysql start

导入数据

$ mysql -u root -p
mysql> create database test;
mysql> use test;
mysql> set names utf8;
mysql> source /path/to/test-tables.sql;

或者

$ mysql -u root -p test < /path/to/test-tables.sql

pymysql简单使用

创建数据库

pymysql.connect(host='127.0.0.1', user='test', passwd='', use_unicode=True)
cursor = self.connect.cursor()
cursor.execute("create database if not exists sql-test")

选择数据库
```
self.cursor.execute("use sql-test;")
```

创建表

sql = """create table if not exists saes(
  pos varchar(20),
  area varchar(20),
  name varchar(100),
  time varchar(20));"""
cursor.execute(sql)

更新数据

cursor.execute("""select * from saes where name = %s""", item["name"])
ret = cursor.fetchone()
if ret:
  cursor.execute(
      """update saes set pos = %s,area = %s,
          name = %s,time = %s
          where name = %s""",
      (item['pos'],
      item['area'],
      item['name'],
      item['time'],
      item['name']))
else:
  cursor.execute(
      """insert into saes(pos,area,cku,name,time)
      value (%s,%s,%s,%s)""",
      (item['pos'],
      item['area'],
      item['name'],
      item['time']))
connect.commit()

删除表
```
drop table tablename;
```

创建表

mysql> CREATE TABLE students (
    -> id bigint(20) NOT NULL AUTO_INCREMENT,
    -> name varchar(100) NOT NULL,
    -> gender varchar(1) NOT NULL,
    -> score int(11) NOT NULL,
    -> PRIMARY KEY (id)
    -> ) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;

指定字符集为 utf8

其他命令

create database new_dbname;--新建数据库
drop database old_dbnane; --删除数据库
show databases;--显示数据库
use databasename;--使用数据库
select database();--查看已选择的数据库

show tables;--显示当前库的所有表
create table tablename(fieldname1 fieldtype1,fieldname2 fieldtype2,..)[ENGINE=engine_name];--创建表
drop table tablename; --删除表
create table tablename select statement;--通过子查询创建表
desc tablename;--查看表结构
show create table tablename;--查看建表语句

alter table tablename add new_fielname new_fieldtype;--新增列
alter table tablename add new_fielname new_fieldtype after 列名1;--在列名1后新增列
alter table tablename modify fieldname new_fieldtype;--修改列
alter table tablename drop fieldname;--删除列
alter table tablename_old rename tablename_new;--表重命名

insert into tablename(fieldname1,fieldname2,fieldnamen) valuse(value1,value2,valuen);--增
delete from tablename [where fieldname=value];--删
update tablename set fieldname1=new_value where filename2=value;--改
select * from tablename [where filename=value];--查

truncate table tablename;--清空表中所有数据，DDL语句

show engines;--查看mysql现在已提供的存储引擎:
show variables like '%storage_engine%';--查看mysql当前默认的存储引擎
show create table tablename;--查看某张表用的存储引擎（结果的"ENGINE="部分）
alter table tablename ENGINE=InnoDB--修改引擎
create table tablename(fieldname1 fieldtype1,fieldname2 fieldtype2,..) ENGINE=engine_name;--创建表时设置存储引擎