django 项目中mysql 的编码，数据库迁移问题

以管理员的身份进入cmd 

net start mysql

mysql -u root -p

没有密码直接回车，进入mysql可以创建数据库，

如退出mysql  执行 q：命令

创建数据库  记得指定编码    create database orm_1128 character set utf8;  orm_1128是数据库名字

修改数据库的字符集mysql>use mydb

mysql>alter database mydb character set utf8;

如果报错，

ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: YES)

是因为在mysql5.6版本以后，就需要输入密码了，

设置新密码，123，下次再登录的时候就要输入密码123，

mysql> set password for root@localhost = password('123');
Query OK, 0 rows affected, 1 warning (0.29 sec)

=====

查看数据库  ，可以看到已经创建的表

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| bookmanage1        |
| bookmanage2        |
| db1                |
| db2                |
| gu_orm             |
| myorm              |
| mysql              |
| performance_schema |
| s5orm              |
| school             |
| sys                |
+--------------------+
12 rows in set (0.06 sec)

选择自己要修改的编码的  数据库，然后可以执行 s; 命令 看到表的数据库的编码等信息，进行修改

mysql> use gu_orm;
Database changed
mysql> s
--------------
mysql  Ver 14.14 Distrib 5.7.18, for Win64 (x86_64)

Connection id:          70
Current database:       gu_orm
Current user:           root@localhost
SSL:                    Not in use
Using delimiter:        ;
Server version:         5.7.18 MySQL Community Server (GPL)
Protocol version:       10
Connection:             localhost via TCP/IP
Server characterset:    latin1
Db     characterset:    latin1
Client characterset:    gbk--------------------------------------------------------------
Conn.  characterset:    gbk-----------------------------------------------------------------------
TCP port:               3306
Uptime:                 14 hours 39 min 56 sec

Threads: 4  Questions: 860  Slow queries: 0  Opens: 365  Flush tables: 1  Open tables: 256  Queries per second avg: 0.016
--------------

mysql> set character_set_client=utf8;------修改编码
Query OK, 0 rows affected (0.05 sec)

创建表后如果出错---

  File "C:Python36libsite-packagesdjangodbackendsmysqlase.py", line 30, in <module>
    'Did you install mysqlclient or MySQL-python?' % e
django.core.exceptions.ImproperlyConfigured: Error loading MySQLdb module: No module named 'MyS
QLdb'.
Did you install mysqlclient or MySQL-python?

C:UserslenovoPycharmProjectsgu_ORM_11month>

没有mysqldb（驱动）？？？

在python2之前的版本中是MySQLdb支持，到python3以后都用pymsql,

只需要调一下，在项目的下的__init__.py文件中 导入 import pymsql

写上 pymysql.install_as-MySQLdb() ,就行，

在创建一对多的表的时候，记得把主表，一 的表放在 多 的表前面，要不生成数据库时会报错

执行python manage.py makemigrations 

python manage.py migrate

创建好数据库以后，可以在cmd里看下数据库，

use 数据库名字  ，进入数据库， s 命令查看数据库信息

show tables；  查看表

mysql> use gu_ORM
Database changed
mysql> show table
    -> ;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '' at line 1
mysql> show tables;
+----------------------------+
| Tables_in_gu_orm           |
+----------------------------+
| auth_group                 |
| auth_group_permissions     |
| auth_permission            |
| auth_user                  |
| auth_user_groups           |
| auth_user_user_permissions |
| django_admin_log           |
| django_content_type        |
| django_migrations          |
| django_session             |
| gu_orm_book                |
| gu_orm_publish             |
+----------------------------+
12 rows in set (0.00 sec)

看到这里，就说明已经与数据库连接上了，与pycharm里的表一样

但每次都在cmd查数据不方便，就可以在pycharm里设置，

表就会出现，apply ，OK ，可以使用了

 一对多的表，先对一 的表插入数据，然后在多的表才能插入数据，因为先对多的表插入数据时，有一个外键，需要数据，所以先对一 的表插入数据，

关于数据库的编码问题

 show create table 数据库的表名；  查看 表的编码

alter table 数据库的表名 charset utf8；  修改表的编码

-------

重新迁移数据库时会发生的错误，

C:UserslenovoPycharmProjectsgu_ORM_11month>python manage.py makemigrations
No changes detected

记得在后面加上app名字

C:UserslenovoPycharmProjectsgu_ORM_11month>python manage.py makemigrations gu_orm
Migrations for 'gu_orm':
  gu_ormmigrations001_initial.py
    - Create model Book
    - Create model Publish
    - Add field pu

blish to book

在执行python manage.py migrate

C:UserslenovoPycharmProjectsgu_ORM_11month>python manage.py migrate
Operations to perform:
  Apply all migrations: admin, auth, contenttypes, gu_orm, sessions
Running migrations:
  Applying contenttypes.0001_initial... OK
  Applying auth.0001_initial... OK
  Applying admin.0001_initial... OK
  Applying admin.0002_logentry_remove_auto_add... OK
  Applying contenttypes.0002_remove_content_type_name... OK
  Applying auth.0002_alter_permission_name_max_length... OK
  Applying auth.0003_alter_user_email_max_length... OK
  Applying auth.0004_alter_user_username_opts... OK
  Applying auth.0005_alter_user_last_login_null... OK
  Applying auth.0006_require_contenttypes_0002... OK
  Applying auth.0007_alter_validators_add_error_messages... OK
  Applying auth.0008_alter_user_username_max_length... OK
  Applying gu_orm.0001_initial... OK
  Applying sessions.0001_initial... OK