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Django query for database operation

Django provides a NoSQL query means it not support SQL, We will write queries in Object patterns using python script.

Now I am discussing queries into Django that can be used to implement database operations.

First Create Model Class and define columns according to requirements.


class Student(models.Model):
   rno = Model.CharField(max_length=50)
  sname = Model.CharField(max_length=50)

command 

python manage.py makemigrations appname 
python manage.py migrate

If you want to run the query using Python Shell then first use the following command?

python manage.py shell


1)  Django query for data insertion:-

   ref =  ModelClass(variable1=value,variable2=value)
   ref.save()


 according to Student Model class

 obj = Student(rno='1001',sname='xyz')
 obj.save()


2)  Django query for data updation:

for updation , we will perform two operations first find the row  then update the row

 ref = ModelClassName.objects.get(pk=value)  # find row to update
 ref.columnname = value
   ...
 ref.save()

Example for Student Model Class:-

     s =  Student.objects.get(pk=value)
     s.rno=newvalue
     s.sname=newvalue
     s.save() 

3)  Django query for data deletion:-
    for deletion,we will perform two operations first find row then delete row

    ref = ModelClassname.objects.get(pk=value)
    ref.delete()

   for Student Class, this Query will be implemented this way:-

    s = Student.objects.get(pk=value)      #  display data in Object
    s.delete()


4)  Django query for data selection:-
    
ref = ModelClassName.objects.all()    #for Selection


    Example into Student Class

      s = Student.objects.all()   # display data in QuerySet

5)  Django query for data selection according to a column name

ref = ModelClassName.objects.filter(columnname=value)

for Student Class
s = Student.objects.filter(colname=value)   #display Data in QuerySet



6) Django Query to find a record based on pattern matching similar to LIKE Operator of SQL:-

ref = ModelClassName.objects.filter(colunname__startsWith='char')


for Student Class

obj = Student.objects.filter(sname__startsWith='s')


7) Django Query to find a record based on pattern matching similar to LIKE Operator of SQL:-

ref = ModelClassName.objects.filter(colunname__endsWith='char')

for Student Class

obj = Student.objects.filter(sname__endsWith='s')

8) Django Query to display record using Order based on ascending and descending order?

ref = ModelClassName.objects.order_by('-fees')[:2]

to implement ModelClassname

obj = Student.objects.order_by('-fees')[:2]











   
       

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