<Django>ORM

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ORM 

Import pymysql 

pymysql.connect ( 
	... 
		... 
) 

	1. different programmers write SQL uneven level 
	2. The efficiency is also uneven 

python syntax - automatic translation -> SQL statements 

jQuery the DOM 
$ ( "# d1") - automatic translation -> document.getElementById ( "d1") 

ORM: 
advantages: 
	1. simple, do not write your own SQL statements 
	2. development of high efficiency 
disadvantages: 
	1. you remember this special syntax 
	2 with respect to some of the great God SQL statements, certainly the efficiency gap 

correspondence between the ORM: 
class ---> data table 
objects ---> data line 
properties ---> field 

ORM thing to do: 
1. operating data table -> create table / delete tables / modify table 
operation models.py inside the class 

2. operation data lines -> additions and deletions to change search data 

can not create the database, create the database yourself 

ORM detailed steps to use Django's: 
1 . create the database yourself
create database database name; 
2. Set the database connection configuration Django projects (to tell which one is connected Django database) 
# database relevant configuration 
DATABASES = { 
	'default': { 
		'ENGINE': 'django.db.backends.mysql ', database connection type # 
		' HOST ':' 127.0.0.1 ', connected to the address database # 
		' pORT ': 3306, # ports 
		' nAME': "baidu", # database name 
		'USER': 'root', # users 
		'pASSWORD': 'root' # password 
	} 
} 
3. tell Django with pymysql instead of the default MySQLDB 
connect to the MySQL database in the project / __init__.py file, write the following two: 
Import pymysql 
# pymysql tell Django to use instead of the default MySQLdb 
pymysql.install_as_MySQLdb () 
4. define a class in the following models.py app file, this class must inherit models.Model 


class class name (models.Model): 
	...


The two command execution
1.python3 manage.py makemigrationspy makemigrations
2.python3 manage.py migrate

Increase ORM and single-table queries :( delete, annotate only correspondence between the models is generated in the implementation of the migration, the migration) 
1. Query 
models.UserInfo.objects.all () 

2. increase 
models.UserInfo.objects.create (name = "John Doe") 
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