Eleven .Django one table OneToOneField (ORM)

.ORM a one-meter (OneToOneField)

1. Create the ORM table

And many-to-one relationship is very similar to the relationship. If you define a OneToOneField in the model, the model will be an example of the model through a simple attribute of the model associated with access.

class Person(models.Model):
    name = models.CharField(max_length=20)


class PersonDetail(models.Model):
    age = models.IntegerField(10)
    email = models.EmailField()
　　person = models.OneToOneField(Person)　# person = models.ForeignKey(Person, unique=True)  

2. Query

DEF One (Request): 

　　# query user information alex 
    # forward queries 
    RET = models.PersonDetail.objects.get (the above mentioned id = 1) #   RET = models.PersonDetail.objects.get (the above mentioned id = models.Person.objects.get (name = 'Alex'). ID) 
　　# Person here is a foreign key field in the table is not the class name 
    Print (ret.person)   # the Person Object of the Person object encapsulates 
    Print (ret.person.name, ret.age , ret.email)
 

　　# query user information alex 
    # reverse lookup 
    obj = models.Person.objects.get (name = ' alex ' )
     # personDetail class name in lowercase 
    Print (obj.persondetail)   # personDetail Object 
    Print(obj.name, obj.persondetail.email, obj.persondetail.age)
    return HttpResponse('OK')

Reverse "query is different. Association model one to one relationship also has a manager object, but the manager represents a collection of objects rather than a single object. 

Is ForeignKey on the principle of one-way + unique = True. but since it is a foreign key query then the reverse should be one to one-to-many reverse lookup same way, 

but in fact not the case, one-way reverse lookup is obj.persondetail object. class name in lowercase, no _set.

 

 

 

3. one table (case CRUD)

from django.db Import Models
 # parent table 
class Colors (models.Model): 
    Colors = models.CharField (MAX_LENGTH = 10 ) 
     DEF  __str__ (Self):
         return self.colors 

# -one relationship, only one each of a ball colors, each ball has only one 
class ball (models.Model):
     # color of the ball-one correspondence with the color of the parent table color 
    ball_color = models.OneToOneField ( ' colors ' )  
     # description 
    description = models.CharField (max_length = 10 ) 
  
    DEF  __str__ (Self):
         return self.description

Query data

Table query sub-alphabet:


 from myApp.models Import Colors, Ball
 
Method a: forward lookup 

# inquiry "ball No. 1" corresponding to the color 
# obtain a child table object 
>>> B = Ball.objects.get (Description = " ball No. 1 " )
 <ball: ball No. 1>


 # obtain a corresponding master table object
 
>>> b.ball_color
 <Colors: Red>


method two: reverse lookup

# 获取“1号球”的 Colors 对象
>>> c = Colors.objects.get(ball__description="1号球")
<Colors: red>

>>> c.colors 'red' 

 

Parent table query sub-tables:

 Method a: Reverse Lookup
 #query corresponding to red ball description
#obtain an Object Colors
>>> C = Colors.objects.get (= Colors"Red")
<Colors: Red>#obtain a corresponding ball objects
#where the default lowercase names of sub-tables, if use is set related_name related_name
>>>c.ball
<ball: ball No. 1>

Method two: forward lookup

# 获取颜色为红的 Ball 对象
>>> b = Ball.objects.get(ball_color__colors="red")
<Ball: 1号球> >>> b.description '1号球'

adding data

# Create a new Colors object is 
c = Colors.objects.create (Colors = " Blue " ) 

# create a new Object Ball 
Ball.objects.create (ball_color = c, the Description = " 2 balls " )

delete data

# Delete a Ball objects 
Ball.objects.get (the Description = " 2 balls " ) .Delete () 

# remove a Colors objects 
Colors.objects.get (Colors = " Blue " ) .Delete () 

# Empty a table 
Colors.objects.all (). delete ()

change the data

c = Colors.objects.get(colors="red")
c.colors = 'yellow'
c.save()

# save() 方法

c = Colors.objects.create(colors="green")
b = Ball.objects.get(description="1号球")

b.color = c
b.description = "3号球"
b.save()

# Filter () method 

B = Ball.objects.filter (Description = " 3 Ball " ) 

# Note: update () and delete () method is QuerySet 
b.update (C = ball_color, Description = " Number 1 Ball " )