pycharm 使用ORM建立數據庫

數據表的建立

表的建立

在models.py文件裏面建立數據表類，

from django.db import models
class userinfo(models.Model):
    uid = models.AutoField(primary_key=True)
    username = models.CharField(max_length=32)
    password = models.CharField(max_length=64)

在終端執行數據庫建立命令

python3 manage.py makemigrations
python3 manage.py migrate

這裏須要注意的是，要在setting裏面配置上你的程序，以下圖

執行完成後，能夠登陸到數據庫中，查看是否有你建立的數據庫表

表的更新

把username 字段修改成user字段，如何操做？

from django.db import models
class userinfo(models.Model):
    uid = models.AutoField(primary_key=True)
    user = models.CharField(max_length=32)
    password = models.CharField(max_length=64)

執行數據庫生成命令，能夠看到這裏會有提高，詢問是否要把那個表下面的那個字段要作調整，這裏咱們選擇Y，回車操做 繼續執行下面的命令：

C:\Users\Tony\PycharmProjects\LearnDjango>python3 manage.py makemigrations
Did you rename userinfo.username to userinfo.user (a CharField)? [y/N]

C:\Users\Tony\PycharmProjects\LearnDjango>python3 manage.py migrate
Operations to perform:
  Apply all migrations: admin, app01, sessions, auth, contenttypes
Running migrations:
  Rendering model states... DONE
  Applying app01.0002_auto_20180115_1735... OK

能夠看到結果是修改了的

添加字段的默認值

若是咱們添加一個字段默認沒有給值，則在執行數據庫migrations的時候是會有提高，提示結果以下：

C:\Users\Tony\PycharmProjects\LearnDjango>python3 manage.py makemigrations
You are trying to add a non-nullable field 'age' to userinfo without a default; we can't do that (the database needs something to populate existing ro
ws).
Please select a fix:
 1) Provide a one-off default now (will be set on all existing rows)
 2) Quit, and let me add a default in models.py
Select an option:

解決方法：
咱們選擇2取消這個提示，這個時候，咱們有兩種方法解決：
第一種就是設置一個默認值default

from django.db import models
class userinfo(models.Model):
    uid = models.AutoField(primary_key=True)
    user = models.CharField(max_length=32)
    password = models.CharField(max_length=64)
    age = models.IntegerField(default=1)

第二種解決方法是，指定null能夠爲空
age = models.IntegerField(null=True)