django orm 语句

# 添加数据
    # models.表对象.objects.方法
    models.classes.objects.create(classname='周末一期')
    li = [
        models.classes(classname='周末二期'),
        models.classes(classname='周末三期'),
        models.classes(classname='周末四期'),
    ]
    models.classes.objects.bulk_create(li)

    # 查询数据
    # 获取所有的数据=====> select * from classses;
    res = models.classes.objects.all()
    <QuerySet [
              <classes: classes object (1)>,
              <classes: classes object (2)>,
              <classes: classes object (3)>,
              <classes: classes object (4)>
    ]>
    for item in res:
        print(item.id , item.classname)

    # 获取classname    ====> select classname from classses;
    <QuerySet [
          {'classname': '周末一期'},
          {'classname': '周末二期'},
          {'classname': '周末三期'},
          {'classname': '周末四期'}]>
    res = models.classes.objects.values('classname').all()
    print(res)

    for item in res:
        print(item['classname'])

    # value_list:
    # <QuerySet [('周末一期',), ('周末二期',), ('周末三期',), ('周末四期',)]>
    res = models.classes.objects.values_list('classname').all()
    print(res)

    # 取第一条  ==》 select * from classes limit 1;
    res = models.classes.objects.first()
    print(res.classname)

    # 根据条件查询数据
    res = models.classes.objects.filter(id=4)

    # 删除  ===》 delete from classes where id=1;
    models.classes.objects.filter(id=4).delete()

    # 更新
    models.classes.objects.filter(id=3).update(classname='周末3期')

    # 一对多添加
    models.students.objects.create(student_name='王刚蛋', classes_id=1)
    models.students.objects.create(student_name='王铁锤', classes_id=2)
    models.students.objects.create(student_name='二狗', classes_id=3)
    models.students.objects.create(student_name='刘dd', classes_id=1)
    models.students.objects.create(student_name='狗剩子', classes_id=2)
    models.students.objects.create(student_name='铁蛋', classes_id=3)
    models.students.objects.create(student_name='xxxx', classes_id=3)

    # 正向查询
    # 外键(FK) classes_id 代之===>   classes表里面的一行记录
    # select * from classes left join students on claess.id =stdents.classid;
    # SELECT `app01_students`.`id`, `app01_students`.`student_name`, `app01_students`.`classes_id` FROM `app01_students`
    res = models.students.objects.all()
    for item in res:
        print(item.id, item.student_name,  item.classes.classname)

    # 周末一期有多少学生？
    # obj.表名_set.all()
    # 反向查询
    # select * from classes where classname='周末一期'
    # id  classname
    res = models.classes.objects.filter(classname='周末一期').first()
    select * from students where classes_id =  res['id']
    info = res.students_set.all()
    print(info)
    for item in info:
        print(item.student_name)



    # __ 神奇的双下划线
    res = models.students.objects.filter(classes__classname='周末一期').all()
    # SELECT `app01_students`.`id`,
    #        `app01_students`.`student_name`,
    #         `app01_students`.`classes_id`
    # FROM `app01_students` INNER JOIN `app01_classes` ON (`app01_students`.`classes_id` = `app01_classes`.`id`) WHERE `app01_classes`.`classname` = 周末一期
    print(res.query)
    for item in res:
        print(item.student_name)



    # 获取个数 ===> count() ==> select count(*) from  students
    cnt = models.classes.objects.count()
    print(cnt)


    # 大于，小于
    # greater then
    res = models.classes.objects.filter(id__gt=1)
    res = models.classes.objects.filter(id__gte=1)
    res = models.classes.objects.filter(id__lt=1)
    res = models.classes.objects.filter(id__lte=1)
    # select * from classes where id < 10 and id > 1
    res = models.classes.objects.filter(id__lt=10, id__gt=1)   # 获取id大于1 且 小于10的值

    # in
    # exclude : 除去xxx ,还剩xxxx
    res = models.classes.objects.filter(id__in=[11, 22, 33])   # 获取id等于11、22、33的数据
    res = models.classes.objects.exclude(id__in=[11, 22, 33])  # not in

    #isnull
    res = models.classes.objects.filter(id__isnull=True)

    # select * from stundets where student_name like '%二%';
    # contains
    # startswith == > like 'ven%'，istartswith, endswith ===> like '%ven', iendswith,
    res = models.classes.objects.filter(classname__contains="ven")
    res = models.classes.objects.filter(classname__icontains="ven") # icontains大小写不敏感
    models.classes.objects.exclude(classname__icontains="ven")

    # range
    res = models.classes.objects.filter(id__range=[1, 2])   # 范围bettwen and

    #order by
    #
    models.classes.objects.filter(name='seven').order_by('id')  # asc 升序
    models.Tb1.objects.filter(name='seven').order_by('-id')   # desc 降序

    # group by
    from django.db.models import Count, Min, Max, Sum
    res = models.students.objects.values('classes_id').annotate(c=Count('id'))
    # SELECT `app01_students`.`classes_id`,
    # COUNT(`app01_students`.`id`) AS `c` FROM `app01_students` GROUP BY `app01_students`.`classes_id` ORDER BY NULL

    # limit 、offset

    res = models.Tb1.objects.all()[10:20]

    print(res)

    print(res.query)


    # F
    from django.db.models import F
    models.test.objects.filter(id=1).update(age=F('age') + 1)

    from django.db.models import F, Q
    # Q
    #
    # 方式一：
    Q(nid=8) | Q(nid__gt=10)
    res = models.students.objects.filter(Q(id=8) | Q(id__gt=10))
    # SELECT `app01_students`.`id`, `app01_students`.`student_name`, `app01_students`.`classes_id` FROM `app01_students` WHERE (`app01_students`.`id` = 8 OR `app01_students`.`id` > 10)


    Q(Q(nid=8) | Q(nid__gt=10)) & Q(caption='root')
    res = models.students.objects.filter(Q( Q(id=8) | Q(id__gt=10)) & Q(student_name='root'))
    # SELECT `app01_students`.`id`, `app01_students`.`student_name`, `app01_students`.`classes_id` FROM `app01_students` WHERE ((`app01_students`.`id` = 8 OR `app01_students`.`id` > 10) AND `app01_students`.`student_name` = root)
    print(res.query)




    # 执行原生SQL

    from django.db import connection, connections
    cursor = connection.cursor()
    cursor = connections['xxx'].cursor()


    # cursor.execute("""SELECT * from auth_user where id = %s""", [1])
    row = cursor.fetchone()

    # 伪代码
    # 伪代码
    # 1. 反向查询
    res = models.teacher.objects.filter(tname='eagon').first()
    info = res.teacher2class_set().all()
    for item in info:
        item.classes.classname

    # 2. 查询
    res = models.teacher2class.objects.filter(teacher__tname='eagon')
    for item in res:
        item.classes.classname