django開發系列:ORM之作業
模型:
from django.db import models
class Student(models.Model):
name = models.CharField(max_length=100)
gender = models.SmallIntegerField()
class Meta:
db_table = 'student'
class Course(models.Model):
name = models.CharField(max_length=100)
teacher = models.ForeignKey("Teacher",on_delete=models.SET_NULL,null=True)
class Meta:
db_table = 'course'
class Score(models.Model):
student = models.ForeignKey("Student",on_delete=models.CASCADE)
course = models.ForeignKey("Course",on_delete=models.CASCADE)
number = models.FloatField()
class Meta:
db_table = 'score'
class Teacher(models.Model):
name = models.CharField(max_length=100)
class Meta:
db_table = 'teacher'
作業:
使用之前學到過的操作實現下面的查詢操作:
1. 查詢平均成績大於60分的同學的id和平均成績;
2. 查詢所有同學的id、姓名、選課的數量、總成績;
3. 查詢姓“李”的老師的個數;
4. 查詢沒學過“李老師”課的同學的id、姓名;
5. 查詢學過課程id爲1和2的所有同學的id、姓名;
6. 查詢學過“黃老師”所教的“所有課”的同學的id、姓名; 7. 查詢所有課程成績小於60分的同學的id和姓名;
8. 查詢沒有學全所有課的同學的id、姓名;
9. 查詢所有學生的姓名、平均分,並且按照平均分從高到低排序;
10. 查詢各科成績的最高和最低分,以如下形式顯示:課程ID,課程名稱,最高分,最低分;
11. 查詢沒門課程的平均成績,按照平均成績進行排序; 12. 統計總共有多少女生,多少男生;
13. 將“黃老師”的每一門課程都在原來的基礎之上加5分;
14. 查詢兩門以上不及格的同學的id、姓名、以及不及格課程數;
15. 查詢每門課的選課人數;
查詢代碼:
from django.shortcuts import render
from django.http import HttpResponse
from .models import Student,Teacher,Score,Course
from django.db.models import Avg,Sum,Count,Q,F,Min,Max
def index(request):
#1. 查詢平均成績大於60分的同學的id和平均成績;
students = Student.objects.annotate(score_avg = Avg("score__number")).filter(score_avg__gt=60).values('id','score_avg')
for student in students:
print(student)
return HttpResponse('123')
def index2(request):
#2. 查詢所有同學的id、姓名、選課的數量、總成績;
students = Student.objects.annotate(course_num = Count('score'),total = Sum('score__number')).values('id','course_num','total','name')
for student in students:
print(student)
return HttpResponse('456')
def index3(request):
#3.查詢姓“李”的老師的個數;
count = Teacher.objects.filter(name__startswith='李').count()
print(count)
return HttpResponse('789')
def index4(request):
#4.查詢沒學過“李老師”課的同學的id、姓名;
students = Student.objects.exclude(score__course__teacher__name = '李老師').values('id','name')
for student in students:
print(student)
return HttpResponse('741')
def index5(request):
# 5.查詢學過課程id爲1和2的所有同學的id、姓名
students = Student.objects.filter(score__course__in=[1.2]).values('id','name')
for student in students:
print(student)
return HttpResponse('852')
def index6(request):
# 6.查詢學過“黃老師”所教的所有課的同學的學號、姓名;
# 1. 首先先找到每一位學生學習的黃老師課程的數量;A
# 2. 在課程的表中找到黃老師教的課程的數量;B
# 3. 判斷A是否等於B,如果相等,那麼意味着這位學生學習了黃老師教的
# 所有課程,如果不想等,那麼意味着這位學生沒有學完黃老師教的所有課程
rows = Student.objects.annotate(nums =Count("score__course",filter=Q(score__course__teacher__name='黃老師'))).filter(nums =Course.objects.filter(teacher__name='黃老師').count()).values('id','name')
for row in rows:
print(row)
return HttpResponse('00000')
def index7(request):
# 7. 查詢所有課程成績小於60分的同學的id和姓名;
students = Student.objects.filter(score__number__lt=60).values('id','name')
print(students)
for student in students:
print(student)
return HttpResponse('159')
def index8(request):
# 8. 查詢沒有學全所有課的同學的id、姓名;
# students = Student.objects.annotate(num=Count(F('score__course')))
students = Student.objects.annotate(num = Count(F('score__course'))).filter(num__lt=Course.objects.count()).values('id','name')
print(students)
return HttpResponse('index8')
def index9(request):
# 9.查詢所有學生的姓名、平均分,並且按照平均分從高到低排序;
students =Student.objects.annotate(avg = Avg('score__course')).order_by('-avg').values('name','avg')
for student in students:
print(student)
return HttpResponse('index9')
def index10(request):
# 10.查詢各科成績的最高和最低分,以如下形式顯示:課程ID,課程名稱,最高分,最低分:
courses = Course.objects.annotate(min = Min("score__number"),max=Max("score__number")).values('id','name','min','max')
for course in courses:
print(course)
return HttpResponse("index10")
def index11(request):
# 11. 查詢每門課程的平均成績,按照平均成績進行排序;
courses = Course.objects.annotate(avg =Avg("score__number")).order_by("avg").values("id",'name','avg')
for course in courses:
print(course)
return HttpResponse('index11')
def index12(request):
# 12. 統計總共有多少女生,多少男生
rows = Student.objects.aggregate(male_num=Count('gender',filter=Q(gender=1)),female_num =Count('gender',filter=Q(gender=2)))
print(rows)
return HttpResponse('index12')
def index13(request):
# 13.將“黃老師”的每一門課程都在原來的基礎之上加5分;
rows = Score.objects.filter(course__teacher__name='黃老師').update(number=F('number')+5)
print(rows)
return HttpResponse('index13')
def index14(request):
#14 .查詢兩門以上不及格的同學的id、姓名、以及不及格課程數
students = Student.objects.annotate(bad_num = Count('score__number',filter=Q(score__number__lt=60))).filter(bad_num__gte=2).values('id','name','bad_num')
for student in students:
print(student)
return HttpResponse('index14')
def index15(request):
#15. 查詢每門課的選課人數;
courses = Course.objects.annotate(student_num = Count('score__student')).values('name','student_num')
for course in courses:
print(course)
return HttpResponse('index15')