Django之ORM操作
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
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)
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
ORM连表查询操作:
1 # 每次循环连表查询 2 # restea = models.teac_clas.objects.filter(teachers_id__tName="武沛齐") 3 # for i in restea: 4 # print(i.teachers_id.tName) 5 #使用values方法直接获取字典无需循环连表 6 # restea = models.teac_clas.objects.filter(teachers_id__tName="武沛齐").values("teachers_id__tName") 7 # for i in restea: 8 # print(i["teachers_id__tName"])
ORM连表示例:
class Boy(models.Model): bname = models.CharField(max_length=10) class Girl(models.Model): gname = models.CharField(max_length=10) class b_g(models.Model): b = models.ForeignKey("Boy") g = models.ForeignKey("Girl") class Mate: unique_bj=[("b","g")] #唯一索引(男生和女生只能唯一匹配)
# 编辑者：闫龙 from django.views import View from django.shortcuts import HttpResponse from appOne import models class TestView(View): def addData(self): girllist=[ models.Girl(gname="小爽"), models.Girl(gname="小红"), models.Girl(gname="小黄"), models.Girl(gname="小白"), ] boylist=[ models.Boy(bname="龙哥"), models.Boy(bname="小明"), models.Boy(bname="小齐"), models.Boy(bname="小杰"), ] models.Girl.objects.bulk_create(girllist) models.Boy.objects.bulk_create(boylist) def get(self,request): #通过关系表,双下划线到boy中获取名称,在通过双下划线到girl中拿到相应的值 #res = models.b_g.objects.filter(b_id__bname="龙哥").values("g_id__gname") # for i in res: # print(i["g_id__gname"]) #通过关系表,双下划綫到boy中获取名称,在通过girl对象索引到相应的值 res = models.b_g.objects.filter(b_id__bname="龙哥") for i in res: print(i.g.gname)#i.g获取girl对象,拿到相应的名字 return HttpResponse(".....")
ORM关系表:
1 from django.db import models 2 # Create your models here. 3 class boys(models.Model): 4 bname = models.CharField(max_length=10) 5 #ManyToManyField是Django内部方法自动生成的关系表(boys_girls) 6 #在数据库中会自动建立一张关系表:boys_bAg 7 bAg = models.ManyToManyField("girls") 8 #ManyToManyField(through)就可以使用自己创建的关系表作为ManyToManyField 9 #但是这种生成方式是存在问题的:无法使用add(),set(),remove()方法,但是可以使用all()和clear()方法 10 bAg = models.ManyToManyField("girls",through="b_g",through_fields=("b","g")) 11 12 class girls(models.Model): 13 gname = models.CharField(max_length=10) 14 15 #如果使用默认生成表,则无需此类 16 class B_G(models.Model): 17 b = models.ForeignKey("boys") 18 g = models.ForeignKey("girls")
1 from appTwo import models 2 from django.views import View 3 from django.shortcuts import HttpResponse 4 class TestView(View): 5 def addData(self): 6 girllist=[ 7 models.girls(gname="小爽"), 8 models.girls(gname="小红"), 9 models.girls(gname="小黄"), 10 models.girls(gname="小白"), 11 ] 12 boylist=[ 13 models.boys(bname="龙哥"), 14 models.boys(bname="小明"), 15 models.boys(bname="小齐"), 16 models.boys(bname="小杰"), 17 ] 18 models.Girl.objects.bulk_create(girllist) 19 models.Boy.objects.bulk_create(boylist) 20 21 def get(self,request): 22 res = models.boys.objects.filter(bname="龙哥").first() 23 girllist = res.bAg.all() #拿到res.id对应在boys_bAg中,对应girl的所有对象 24 for i in girllist: 25 print(i.gname) 26 res.bAg.add(4) 27 #向boys_bAg中加入res.id , 4数据等同于insert into boys_bAg(boys_id,girls_id) values(1,4) 28 res.bAg.remove(2) 29 #删除boys_bAg中boys_id=res.id and girls_id = 2的数据 30 res.bAg.set(2) 31 #清空boys_bAg中所有boys_id=res.id的数据,并插入数据boys_id=res.id,girls_id=2 32 res.bAg.clear() 33 #清空boys_bAg中所有boys_id=res.id的数据 34 return HttpResponse("......")
