python自動化之models 進階操作二

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

def all(self)
    # 獲取所有的數據對象

def filter(self, *args, **kwargs)
    # 條件查詢
    # 條件可以是：參數，字典，Q

def exclude(self, *args, **kwargs)
    # 條件查詢
    # 條件可以是：參數，字典，Q

def select_related(self, *fields)
     性能相關：表之間進行join連表操作，一次性獲取關聯的數據。
     model.tb.objects.all().select_related()
     model.tb.objects.all().select_related('外鍵字段')
     model.tb.objects.all().select_related('外鍵字段__外鍵字段')

def prefetch_related(self, *lookups)
    性能相關：多表連表操作時速度會慢，使用其執行多次SQL查詢在Python代碼中實現連表操作。
            # 獲取所有用戶表
            # 獲取用戶類型表where id in (用戶表中的查到的所有用戶ID)
            models.UserInfo.objects.prefetch_related('外鍵字段')



            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)
    # 用於實現聚合group by查詢

    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)
    # 用於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進行去重

def order_by(self, *field_names)
    # 用於排序
    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)
    # 構造額外的查詢條件或者映射，如：子查詢

    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則是倒序，如果多個排序則一一倒序


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

 def only(self, *fields):
    #僅取某個表中的數據
     models.UserInfo.objects.only('username','id')
     或
     models.UserInfo.objects.filter(...).only('username','id')

 def using(self, alias):
     指定使用的數據庫，參數為別名（setting中的設置）


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

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

    # 如果SQL是其他表時，必須將名字設置為當前UserInfo對象的主鍵列名
    models.UserInfo.objects.raw('select id as nid from 其他表')

    # 為原生SQL設置參數
    models.UserInfo.objects.raw('select id as nid from userinfo where nid>%s', params=[12,])

    # 將獲取的到列名轉換為指定列名
    name_map = {'first': 'first_name', 'last': 'last_name', 'bd': 'birth_date', 'pk': 'id'}
    Person.objects.raw('SELECT * FROM some_other_table', translations=name_map)

    # 指定數據庫
    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):
    # 獲取每行數據為字典格式

def values_list(self, *fields, **kwargs):
    # 獲取每行數據為元祖

def dates(self, field_name, kind, order='ASC'):
    # 根據時間進行某一部分進行去重查找並截取指定內容
    # kind只能是："year"（年）, "month"（年-月）, "day"（年-月-日）
    # order只能是："ASC"  "DESC"
    # 並獲取轉換后的時間
        - 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):
    # 根據時間進行某一部分進行去重查找並截取指定內容，將時間轉換為指定時區時間
    # kind只能是 "year", "month", "day", "hour", "minute", "second"
    # order只能是："ASC"  "DESC"
    # tzinfo時區對象
    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對象


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

def aggregate(self, *args, **kwargs):
   # 聚合函數，獲取字典類型聚合結果
   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):
   # 獲取個數

def get(self, *args, **kwargs):
   # 獲取單個對象

def create(self, **kwargs):
   # 創建對象

def bulk_create(self, objs, batch_size=None):
    # 批量插入
    # batch_size表示一次插入的個數
    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，則獲取，否則，創建
    # defaults 指定創建時，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，則更新，否則，創建
    # defaults 指定創建時或更新時的其他字段
    obj, created = models.UserInfo.objects.update_or_create(username='root1', defaults={'email': '1111111','u_id': 2, 't_id': 1})

def first(self):
   # 獲取第一個

def last(self):
   # 獲取最后一個

def in_bulk(self, id_list=None):
   # 根據主鍵ID進行查找
   id_list = [11,21,31]
   models.DDD.objects.in_bulk(id_list)

def delete(self):
   # 刪除

def update(self, **kwargs):
    # 更新

def exists(self):
   # 是否有結果

其他操作