Python-day60 Object Relational Mapping (ORM) ORM even table query ORM Advanced

ImportOSif __name__=='__main__':    #Specifies the Django project configuration information that the current py script needs to loadOs.environ.setdefault ('Django_settings_module','bookmanagesystem.settings')    #start a Django project    ImportDjango Django.setup () fromApp01ImportModels#Many-to-many operations    #1.create    #have done two things    #1. Created a new author named Ker1 2. Associate the newly created author with the first book    #ret = models. Book.objects.first (). Author.create (    #name= ' Ker1 ',    #age=18,    #phone= ' 1516165 ',    #detail_id=3    # )    #Find all the authors of the first book, and ID    #ret = models. Book.objects.first (). Author.all ()    #ret = models. Book.objects.first (). Author.all (). VALUES (' ID ')    #print (ret)    #2.set    #by setting the author of the first book with IDs 3 and 8    #models. Book.objects.first (). Author.set ([3,8])    #query all the IDs of the first book    #ret = models. Book.objects.first (). Author.all (). VALUES (' ID ')    #print (ret)    #3. Add    #Add an Author object with ID 8 to the first book    #models. Book.objects.first (). Author.add (8)    #ret = models. Book.objects.first (). Author.all (). VALUES (' ID ')    #print (ret)    #4.remove    #Remove the author of the first book with a foreign key ID of 3    #models. Book.objects.first (). Author.remove (3)    #ret = models. Book.objects.first (). Author.all (). VALUES (' ID ')    #print (ret)    #5.clear    #Clear all authors of the first book    #models. Book.objects.first (). Author.clear ()    #ret = models. Book.objects.first (). Author.all (). VALUES (' ID ')    #print (ret)    #6.all    #View all the contents of the first book's Objects    #ret = models. Book.objects.first (). Author.all ()    #print (ret)    #Aggregation    #Check the total price of all books     fromDjango.db.modelsImportAVG, Sum, Max, Min, Count#need to call aggregate (alias = inside write aggregate function (' condition ') before using aggregate function)    #Find out the total price of all the books    #ret = models. Book.objects.aggregate (sum_price=sum (' price '))    #print (ret)    #view average price \ maximum price \ Minimum price    #ret = models. Book.objects.aggregate (Avg_pirce=avg (' price '),    #Max_price=max (' price '),    #min_price=min (' price '))    #print (ret)    #    ## Number of authors per book    #ret = models. Book.objects.annotate (C=count (' author ')). VALUES (' title ', ' C ' )    #print (ret)    #    ## Count the prices of the cheapest books that each publisher buys    #ret = models. Publisher.objects.annotate (min_price=min (' Books__price ')). VALUES (' name ', ' Min_price ')    #print (ret)    #count more than one author's book (The number of authors is greater than 1)    #ret = models. Book.objects.annotate (C=count (' author ')). Filter (C__gt=1)    #print (ret)    #Sort by the number of book authors    #ret = models. Book.objects.annotate (C=count (' author ')). order_by (' C ' )    #print (ret)    #Query the total price of each author's books Book__price All prices in the Book table    #ret = models. Author.objects.annotate (sum_price=sum (' Book__price ')). VALUES (' name ', ' Sum_price ')    #print (ret)

Python-day60 Object Relational Mapping (ORM) ORM even table query ORM Advanced