Django之ORM操作

Posted 2020-09-25 DragonFire

ORM基本增删改查操作:

 1 # 增
 2 models.Tb1.objects.create(c1=‘xx‘, c2=‘oo‘)  增加一条数据，可以接受字典类型数据 **kwargs
 3 obj = models.Tb1(c1=‘xx‘, c2=‘oo‘)
 4 obj.save()
 5 
 6 # 查
 7 models.Tb1.objects.get(id=123)         # 获取单条数据，不存在则报错（不建议）
 8 models.Tb1.objects.all()               # 获取全部
 9 models.Tb1.objects.filter(name=‘seven‘) # 获取指定条件的数据
10 models.Tb1.objects.exclude(name=‘seven‘) # 获取指定条件的数据
11 
12 # 删
13 models.Tb1.objects.filter(name=‘seven‘).delete() # 删除指定条件的数据
14 
15 # 改
16 models.Tb1.objects.filter(name=‘seven‘).update(gender=‘0‘)  # 将指定条件的数据更新，均支持 **kwargs
17 obj = models.Tb1.objects.get(id=1)
18 obj.c1 = ‘111‘
19 obj.save()# 修改单条数据

增删改查

ORM进阶操作:

# 获取个数
models.Tb1.objects.filter(name=‘seven‘).count()

# 大于，小于
models.Tb1.objects.filter(id__gt=1)              # 获取id大于1的值
models.Tb1.objects.filter(id__gte=1)              # 获取id大于等于1的值
models.Tb1.objects.filter(id__lt=10)             # 获取id小于10的值
models.Tb1.objects.filter(id__lte=10)             # 获取id小于10的值
models.Tb1.objects.filter(id__lt=10, id__gt=1)   # 获取id大于1 且 小于10的值

# in
models.Tb1.objects.filter(id__in=[11, 22, 33])   # 获取id等于11、22、33的数据
models.Tb1.objects.exclude(id__in=[11, 22, 33])  # not in

# isnull
models.Entry.objects.filter(pub_date__isnull=True)

# contains()
models.Tb1.objects.filter(name__contains="ven")
models.Tb1.objects.filter(name__icontains="ven") # icontains大小写不敏感
models.Tb1.objects.exclude(name__icontains="ven")

# range
models.Tb1.objects.filter(id__range=[1, 2])   # 范围bettwen and

# 其他类似
#startswith，istartswith, endswith, iendswith,

# order by
models.Tb1.objects.filter(name=‘seven‘).order_by(‘id‘)    # asc
models.Tb1.objects.filter(name=‘seven‘).order_by(‘-id‘)   # desc

# group by
from django.db.models import Count, Min, Max, Sum
models.Tb1.objects.filter(c1=1).values(‘id‘).annotate(c=Count(‘num‘))
#SELECT "app01_tb1"."id", COUNT("app01_tb1"."num") AS "c" FROM "app01_tb1" WHERE "app01_tb1"."c1" = 1 GROUP BY "app01_tb1"."id"

# limit 、offset
models.Tb1.objects.all()[10:20]

# regex正则匹配，iregex 不区分大小写
models.Entry.objects.get(title__regex=r‘^(An?|The) +‘)
models.Entry.objects.get(title__iregex=r‘^(an?|the) +‘)

# date
import datetime
models.Entry.objects.filter(pub_date__date=datetime.date(2005, 1, 1))
models.Entry.objects.filter(pub_date__date__gt=datetime.date(2005, 1, 1))

# year
models.Entry.objects.filter(pub_date__year=2005)
models.Entry.objects.filter(pub_date__year__gte=2005)

# month
models.Entry.objects.filter(pub_date__month=12)
models.Entry.objects.filter(pub_date__month__gte=6)

# day
models.Entry.objects.filter(pub_date__day=3)
models.Entry.objects.filter(pub_date__day__gte=3)

# week_day
models.Entry.objects.filter(pub_date__week_day=2)
models.Entry.objects.filter(pub_date__week_day__gte=2)

# hour
models.Event.objects.filter(timestamp__hour=23)
models.Event.objects.filter(time__hour=5)
models.Event.objects.filter(timestamp__hour__gte=12)

# minute
models.Event.objects.filter(timestamp__minute=29)
models.Event.objects.filter(time__minute=46)
models.Event.objects.filter(timestamp__minute__gte=29)

# second
models.Event.objects.filter(timestamp__second=31)
models.Event.objects.filter(time__second=2)
models.Event.objects.filter(timestamp__second__gte=31)

进阶操作

ORM高级操作(Q,F,extra,原生SQL)

#extra
#extra(self, select=None, where=None, params=None, tables=None, order_by=None, select_params=None)
models.Entry.objects.extra(select={‘new_id‘: "select col from sometable where othercol > %s"}, select_params=(1,))
#select *,(select col from sometable where otherco >1) as new_id from Entry
models.Entry.objects.extra(where=[‘headline=%s‘], params=[‘Lennon‘])
#select * from Entry where headline=‘Lennon‘
models.Entry.objects.extra(where=["foo=‘a‘ OR bar = ‘a‘", "baz = ‘a‘"])
#select * from Entry where foo=‘a‘ or bar = ‘a‘ and baz=‘a‘
models.Entry.objects.extra(select={‘new_id‘: "select id from tb where id > %s"},
                           select_params=(1,), order_by=[‘-nid‘])
#select *,(select id from tb where id > 1) from Entry order nid desc

#F
from django.db.models import F
models.Tb1.objects.update(num=F(‘num‘)+1)
#先引用(F(‘num‘)+1  用来将原始值取出并+1),再赋值(num=F(‘num‘)+1)相当于,num+1之后更新


#Q
from django.db.models import Q
#方式一：
Q(nid__gt=10)
#where nid > 10
Q(nid=8) | Q(nid__gt=10)
#where nid =8 or nid >10
Q(Q(nid=8) | Q(nid__gt=10)) & Q(caption=‘root‘)
# where nid = 8 or nid>10 and caption=‘root‘
#方式二：
con = Q()
q1 = Q()
q1.connector = ‘OR‘
q1.children.append((‘id‘, 1))
q1.children.append((‘id‘, 10))
q1.children.append((‘id‘, 9))
# q1 : where id =1 or id=10 or id=9 
q2 = Q()
q2.connector = ‘OR‘
q2.children.append((‘c1‘, 1))
q2.children.append((‘c1‘, 10))
q2.children.append((‘c1‘, 9))
#q2 :where c1=1 or c1=10 or c1=9
con.add(q1, ‘AND‘)
con.add(q2, ‘AND‘)
#con: where (id =1 or id=10 or id=9 ) and (c1=1 or c1=10 or c1=9)
models.Tb1.objects.filter(con)
#select * from Tb1 where (id =1 or id=10 or id=9 ) and (c1=1 or c1=10 or c1=9)

# 执行原生SQL
from django.db import connection, connections
cursor = connection.cursor()  
#拿到默认数据库default连接的游标
cursors = connections[‘db1‘].cursor()
#拿到指定数据库db1的游标
cursor.execute("""SELECT * from auth_user where id = %s""", [1])
row = cursor.fetchone()

ORM高阶操作

ORM其他操作(ORM对象方法拆解)

##################################################################
# PUBLIC METHODS THAT ALTER ATTRIBUTES AND RETURN A NEW QUERYSET #
##################################################################

def all(self)
    # 获取所有的数据对象

def filter(self, *args, **kwargs)
    # 条件查询
    # 条件可以是：参数，字典，Q

def exclude(self, *args, **kwargs)
    # 条件查询
    # 条件可以是：参数，字典，Q

def select_related(self, *fields)
     性能相关：表之间进行join连表操作，一次性获取关联的数据。
     model.tb.objects.all().select_related()
     model.tb.objects.all().select_related(‘外键字段‘)
     model.tb.objects.all().select_related(‘外键字段__外键字段‘)

def prefetch_related(self, *lookups)
    性能相关：多表连表操作时速度会慢，使用其执行多次SQL查询在Python代码中实现连表操作。
            # 获取所有用户表
            # 获取用户类型表where id in (用户表中的查到的所有用户ID)
            models.UserInfo.objects.prefetch_related(‘外键字段‘)



            from django.db.models import Count, Case, When, IntegerField
            Article.objects.annotate(
                numviews=Count(Case(
                    When(readership__what_time__lt=treshold, then=1),
                    output_field=CharField(),
                ))
            )

            students = Student.objects.all().annotate(num_excused_absences=models.Sum(
                models.Case(
                    models.When(absence__type=‘Excused‘, then=1),
                default=0,
                output_field=models.IntegerField()
            )))

def annotate(self, *args, **kwargs)
    # 用于实现聚合group by查询

    from django.db.models import Count, Avg, Max, Min, Sum

    v = models.UserInfo.objects.values(‘u_id‘).annotate(uid=Count(‘u_id‘))
    # SELECT u_id, COUNT(ui) AS `uid` FROM UserInfo GROUP BY u_id

    v = models.UserInfo.objects.values(‘u_id‘).annotate(uid=Count(‘u_id‘)).filter(uid__gt=1)
    # SELECT u_id, COUNT(ui_id) AS `uid` FROM UserInfo GROUP BY u_id having count(u_id) > 1

    v = models.UserInfo.objects.values(‘u_id‘).annotate(uid=Count(‘u_id‘,distinct=True)).filter(uid__gt=1)
    # SELECT u_id, COUNT( DISTINCT ui_id) AS `uid` FROM UserInfo GROUP BY u_id having count(u_id) > 1

def distinct(self, *field_names)
    # 用于distinct去重
    models.UserInfo.objects.values(‘nid‘).distinct()
    # select distinct nid from userinfo

    注：只有在PostgreSQL中才能使用distinct进行去重

def order_by(self, *field_names)
    # 用于排序
    models.UserInfo.objects.all().order_by(‘-id‘,‘age‘)

def extra(self, select=None, where=None, params=None, tables=None, order_by=None, select_params=None)
    # 构造额外的查询条件或者映射，如：子查询

    Entry.objects.extra(select={‘new_id‘: "select col from sometable where othercol > %s"}, select_params=(1,))
    Entry.objects.extra(where=[‘headline=%s‘], params=[‘Lennon‘])
    Entry.objects.extra(where=["foo=‘a‘ OR bar = ‘a‘", "baz = ‘a‘"])
    Entry.objects.extra(select={‘new_id‘: "select id from tb where id > %s"}, select_params=(1,), order_by=[‘-nid‘])

 def reverse(self):
    # 倒序
    models.UserInfo.objects.all().order_by(‘-nid‘).reverse()
    # 注：如果存在order_by，reverse则是倒序，如果多个排序则一一倒序


 def defer(self, *fields):
    models.UserInfo.objects.defer(‘username‘,‘id‘)
    或
    models.UserInfo.objects.filter(...).defer(‘username‘,‘id‘)
    #映射中排除某列数据

 def only(self, *fields):
    #仅取某个表中的数据
     models.UserInfo.objects.only(‘username‘,‘id‘)
     或
     models.UserInfo.objects.filter(...).only(‘username‘,‘id‘)

 def using(self, alias):
     指定使用的数据库，参数为别名（setting中的设置）


##################################################
# PUBLIC METHODS THAT RETURN A QUERYSET SUBCLASS #
##################################################

def raw(self, raw_query, params=None, translations=None, using=None):
    # 执行原生SQL
    models.UserInfo.objects.raw(‘select * from userinfo‘)

    # 如果SQL是其他表时，必须将名字设置为当前UserInfo对象的主键列名
    models.UserInfo.objects.raw(‘select id as nid from 其他表‘)

    # 为原生SQL设置参数
    models.UserInfo.objects.raw(‘select id as nid from userinfo where nid>%s‘, params=[12,])

    # 将获取的到列名转换为指定列名
    name_map = {‘first‘: ‘first_name‘, ‘last‘: ‘last_name‘, ‘bd‘: ‘birth_date‘, ‘pk‘: ‘id‘}
    Person.objects.raw(‘SELECT * FROM some_other_table‘, translations=name_map)

    # 指定数据库
    models.UserInfo.objects.raw(‘select * from userinfo‘, using="default")

    ################### 原生SQL ###################
    from django.db import connection, connections
    cursor = connection.cursor()  # cursor = connections[‘default‘].cursor()
    cursor.execute("""SELECT * from auth_user where id = %s""", [1])
    row = cursor.fetchone() # fetchall()/fetchmany(..)


def values(self, *fields):
    # 获取每行数据为字典格式

def values_list(self, *fields, **kwargs):
    # 获取每行数据为元祖

def dates(self, field_name, kind, order=‘ASC‘):
    # 根据时间进行某一部分进行去重查找并截取指定内容
    # kind只能是："year"（年）, "month"（年-月）, "day"（年-月-日）
    # order只能是："ASC"  "DESC"
    # 并获取转换后的时间
        - year : 年-01-01
        - month: 年-月-01
        - day  : 年-月-日

    models.DatePlus.objects.dates(‘ctime‘,‘day‘,‘DESC‘)

def datetimes(self, field_name, kind, order=‘ASC‘, tzinfo=None):
    # 根据时间进行某一部分进行去重查找并截取指定内容，将时间转换为指定时区时间
    # kind只能是 "year", "month", "day", "hour", "minute", "second"
    # order只能是："ASC"  "DESC"
    # tzinfo时区对象
    models.DDD.objects.datetimes(‘ctime‘,‘hour‘,tzinfo=pytz.UTC)
    models.DDD.objects.datetimes(‘ctime‘,‘hour‘,tzinfo=pytz.timezone(‘Asia/Shanghai‘))

    """
    pip3 install pytz
    import pytz
    pytz.all_timezones
    pytz.timezone(‘Asia/Shanghai’)
    """

def none(self):
    # 空QuerySet对象


####################################
# METHODS THAT DO DATABASE QUERIES #
####################################

def aggregate(self, *args, **kwargs):
   # 聚合函数，获取字典类型聚合结果
   from django.db.models import Count, Avg, Max, Min, Sum
   result = models.UserInfo.objects.aggregate(k=Count(‘u_id‘, distinct=True), n=Count(‘nid‘))
   ===> {‘k‘: 3, ‘n‘: 4}

def count(self):
   # 获取个数

def get(self, *args, **kwargs):
   # 获取单个对象

def create(self, **kwargs):
   # 创建对象

def bulk_create(self, objs, batch_size=None):
    # 批量插入
    # batch_size表示一次插入的个数
    objs = [
        models.DDD(name=‘r11‘),
        models.DDD(name=‘r22‘)
    ]
    models.DDD.objects.bulk_create(objs, 10)

def get_or_create(self, defaults=None, **kwargs):
    # 如果存在，则获取，否则，创建
    # defaults 指定创建时，其他字段的值
    obj, created = models.UserInfo.objects.get_or_create(username=‘root1‘, defaults={‘email‘: ‘1111111‘,‘u_id‘: 2, ‘t_id‘: 2})

def update_or_create(self, defaults=None, **kwargs):
    # 如果存在，则更新，否则，创建
    # defaults 指定创建时或更新时的其他字段
    obj, created = models.UserInfo.objects.update_or_create(username=‘root1‘, defaults={‘email‘: ‘1111111‘,‘u_id‘: 2, ‘t_id‘: 1})

def first(self):
   # 获取第一个

def last(self):
   # 获取最后一个

def in_bulk(self, id_list=None):
   # 根据主键ID进行查找
   id_list = [11,21,31]
   models.DDD.objects.in_bulk(id_list)

def delete(self):
   # 删除

def update(self, **kwargs):
    # 更新

def exists(self):
   # 是否有结果

其他操作

其他操作