我有以下代码
#!/usr/bin/env python
"""doc"""
import peewee
db = peewee.SqliteDatabase(":memory:")
class BaseModel(peewee.Model): # pylint: disable=W0232
"""base model"""
class Meta: # pylint: disable=C0111,W0232,R0903
database = db
class Student(BaseModel):
"""doc"""
name = peewee.CharField()
class Course(BaseModel):
"""doc"""
name = peewee.CharField()
class StudentCourse(BaseModel):
"""doc"""
student = peewee.ForeignKeyField(Student)
course = peewee.ForeignKeyField(Course)
Student.create_table()
Course.create_table()
StudentCourse.create_table()
s1 = Student(name="Student1")
s1.save()
s2 = Student(name="Student2")
s2.save()
s3 = Student(name="Student3")
s3.save()
s4 = Student(name="Student4")
s4.save()
c1 = Course(name="course1")
c1.save()
c2 = Course(name="course2")
c2.save()
c3 = Course(name="course3")
c3.save()
sc21 = StudentCourse(student=s2, course=c1)
sc21.save()
sc22 = StudentCourse(student=s2, course=c2)
sc22.save()
sc23 = StudentCourse(student=s2, course=c3)
sc23.save()
sc31 = StudentCourse(student=s3, course=c1)
sc31.save()
sc32 = StudentCourse(student=s3, course=c2)
sc32.save()
sc41 = StudentCourse(student=s4, course=c1)
sc41.save()
query = (
StudentCourse
.select(StudentCourse, Student, Course)
.join(Course)
.switch(StudentCourse)
.join(Student)
.order_by(Student.name))
last = None
for student_course in query:
student = student_course.student
if student != last:
last = student
print "Student: %s" % student.name
print " - %s" % student_course.course.name
产生这个输出：
Student: Student2
- course1
- course2
- course3
Student: Student3
- course1
- course2
Student: Student4
- course1
这基本上是来自peewee docs的示例
我需要过滤结果并仅选择那些拥有给定子集中所有课程的学生：
courses = ["course1", "course2"]
我尝试使用IN运算符并修改选择查询，如下所示：
query = (
StudentCourse
.select(StudentCourse, Student, Course)
.join(Course)
.switch(StudentCourse)
.join(Student)
.where(Course.name << courses)
.order_by(Student.name))
但它会产生错误的结果，这意味着我做错了：
Student: Student2
- course1
- course2
Student: Student3
- course1
- course2
Student: Student4
- course1
这里有两个错误的地方：
- Student2的course3没有打印，我需要它。我认为这是因为course3不在课程列表中。
- Student4被选中，但它不应该被选中，因为Student4没有course1和course2，但course1在课程列表中。
是否有可能在一个查询中实现我想要的，或者我必须遍历学生，为每个学生进行SELECT查询，并将他们的课程列表与我的课程过滤器相匹配？
我的目标是得到这个输出：
Student: Student2
- course1
- course2
- course3
Student: Student3
- course1
- course2