.Django ten single-table operation (ORM)

A single-table operation .ORM --------

1. Create a table orm

python manage.py makemigrations # generate create table script 　　 
python manage.py # generate database table

2 , you must install pymysql pip install pymysql

3 , under the project name __init__ found documents written in it:
 Import pymysql
pymysql.install_as_MySQLdb()

# Models.py 

form django.db Import Models
 class Book (models.Model):　　# table book, django will automatically use the project name + we define the table name 
　　# if there is no custom primary key, django will automatically add a primary key field self-energizing id name 
　　name = models.CharField (= 20 is MAX_LENGTH)　　# field name type name vachar (20 is) 
　　price = models.IntegerField ()　　　# field name type price int 
　　pub_date models.DateField = ()　　　# field name type pub_date date ( timestamp) 
   author = models.CharField (= 32 MAX_LENGTH, null = False)　# default may be empty, can not be set to null = False empty 
　　DEF  __str__ : (self)
　　　　return the self.name　　# display when printing is self instance object. name

 2. CRUD (single table operation) on the data table through the view function

# views.py

from django.shortcuts Import the render
 from app_name.models Import *　　# introduced into the models.py 


DEF the Add (Request):　　# increase view function data 
　　# manner a 
　　b = Book (name = 'python base', price = 99, author = ' Yuan ', pub_date =' 2017-12-12 ' )
　　b.save()

　　# Second way 
　　Book.objects.create (name = 'python base',. Price = 99, author = 'Yuan', pub_date = '2017-12-12' )
　　 # Book.object.create (DIC **) This written # when the value of the to be correspondence table sent by the client, the client can be used directly transmitted dictionary 
　　return the HttpResponse ( ' added successfully ' )
　　


DEF Update (Request):　　# view function to modify data 
　　# manner a 
　　b = Book.objects.get (author = 'yuan ') # Example get the object will get a Book, but when get to zero or more objects when being given 
　　b.price = 109 　　
　　b.save ()　　# this embodiment will be reassigned each field, inefficient 
　　# Second way 
　　Book.objects.filter (author = 'yuan') . update (price = 109) # use QuerySet filter will get a set of objects (which is the book each object instance), because you can get multiple results, based on screening; all for the price of the book was changed to 109 yuan
　　 # would only want to modify the field assignment, efficient

   return the HttpResponse ( ' successfully modified ' )



DEF the Delete (Request):　　# view function to delete data 
　　Book.objects.filter (author = 'Yuan') the Delete ().
       return HttpResponse ( ' deleted successfully ' )

 

 3. query (single table operation) on the data table through the view function

   filter () filter 
   [: 3] taken   
   first () first   
   last () the last    
   values () Returns a collection of object dictionary   
   values_kist () Returns a collection of tuples objects    
   the exclude () does not contain the    
   DISTINCT () remove weight   
   count () Get the total recording number   
   order_by () to sort 
   get () Gets

def select(request):
　　book_list = Book.objects.filter (ID = 2)　　# conditional query returns a collection of objects QuerySet
 
　　book_list Book.objects.all = ()　　# query returns a result of all QuerySet collection object
 
　　book_list = Book.objects.all () [ : 3]　　# slicing operation from the former three; [:: 2] 2 via the steps of taking; [:: --1] backwards take
 
　　book_list Book.objects.first = ()　　# take the first return an instance of the object
 
　　= Book.objects.last book_list ()　　# take returns a last instance object
 
　　book_list = Book.objects.get (ID = 2)　　# conditional query returns a Book when the object instance is not being given only a record taken
 
   book_list = Book .objects.filter (ID = 2) .values ( ' name ' , ' . price ' )   #select name, price form book where id = 2; QuertSet this case returns a collection of objects, but this is a collection of a dictionary object
 
   book_list = Book.objects.filter (ID = 2) .values_list ( ' name ' , ' . price ' )   # SELECT name, form Book. price WHERE ID = 2; QuertSet this case returns a collection of objects, but this is one set of tuple
 
   book_list = Book.objects.exclude (author = ' yuan ' )　　# returns comprising author = 'yuan' of QuerySet that
 
   book_list Book.objects.all = (). values ( ' name ' ) .distinct ()　　# the name deduplication, meaningless without specific fields, because the table has a primary key, not recorded repeat
 
   book_list = Book.objects.all (). cOUNT ()　　# get the number of records returned a number

   book_list = Book.objects.order_by('name')　　# 按name进行排序

　　return render(request,'index.html',{'book_list':book_list})

 4. query (double underlined universal single-table operation) on the data table through the view function

__gt comprising greater than __lt __in comprising less than __icontains not_in __range not included within the scope of   


 Book.objects.filter (price__gt = 50)　　#query the price is greater than 50

Book.objects.filter (name__icontains ='P')　　#query which contains the name of p insensitive; name__contains = 'p' case-sensitive

models.Tb1.objects.filter (id__lt = 10, id__gt = 1)   #acquires id value greater than 1 and less than 10

models.Tb1. objects.filter (id__in= [. 11, 22 is, 33 is])   #Gets the id data equal 11,22,33

models.Tb1.objects.exclude (id__in = [. 11, 22 is, 33 is])  #Not in

models.Tb1. objects.filter (name__contains="Ven")

models.Tb1.objects.filter (name__icontains= " Ven " ) # icontains case insensitive 

models.Tb1.objects.filter (id__range = [. 1, 2])    # range and bettwen
 
startsWith, istartswith, endsWith, iendswith, # starts with, to what end the band i represents not case sensitive 

Book.objects.filter (pub_date__year = 2016)　　# queries all pub_date 2016 record

__exact         exactly equal like ' AAA ' 
__iexact        exactly equal to ignore case iLike ' AAA ' 
__contains      comprises like ' %% AAA ' 
__icontains     comprising ignoring case iLike ' %% AAA ' , but for sqlite, the effect equivalent to icontains contains .
__gt       greater than
 __gte      greater than or equal
 __lt       less than
 __lte      less
 __in       present within a range list
 __startswith     beginning ...
 __istartswith    beginning ... ignore case
 __endswith       to ... end
 __iendswith     Ending ..., ignore case
 __range       within ... range
 __year        year date field
 __month       month date fields
 __day         Day Date field
 __isnull = True / False
 __isnull = True and __exact = None of the difference

 5. Get sql statement corresponding to native orm

  author_obj=models.Author.objects.filter(id=2)

  print(author_obj.query)

Plus settings.py logging in the configuration file, the server can enter a corresponding sql statement orm

Copy the code
# The following code settings.py end of the file is added 

the LOGGING = {
     ' Version ' :. 1 ,
     ' disable_existing_loggers ' : False,
     ' handlers ' : {
         ' Console ' : {
             ' Level ' : ' the DEBUG ' ,
             ' class ' : ' the logging .StreamHandler ' ,
        },
    },
    'loggers': {
        'django.db.backends': {
            'handlers': ['console'],
            'propagate': True,
            'level':'DEBUG',
        },
    }
}