SQLalchemy补充
目录
七 更多查询方式
#1 查询： filer:写条件 filter_by：等于的值
# 查询所有 是list对象
res = session.query(User).all() # 是个普通列表
print(type(res))
print(len(res))
# 2 只查询某几个字段
# select name as xx,email from user;
res = session.query(User.name.label('xx'), User.email)
print(res) # 打出原生sql
print(res.all())
for item in res.all():
print(item[0])
# 3 filter传的是表达式，filter_by传的是参数
res = session.query(User).filter(User.name == "lqz").all()
res = session.query(User).filter(User.name != "lqz").all()
res = session.query(User).filter(User.name != "lqz", User.email == '3@qq.com').all()
#4 django 中使用 Q查询显示 或 非条件 如果是逗号 就是and条件
# flask中，逗号也表示and条件
res = session.query(User).filter_by(name='lqz099').all()
res = session.query(User).filter_by(name='lqz099',email='47@qq.com').all()
# 5 取一个 all了后是list，list 没有first方法
res = session.query(User).first()
# 6查询所有，使用占位符(了解) :value :name
# select * from user where id <20 or name=lqz
res = session.query(User).filter(text("id<:value or name=:name")).params(value=20, name='lqz').all()
# 7 自定义查询（了解）
# from_statement 写纯原生sql
res=session.query(User).from_statement(text("SELECT * FROM users where email=:email")).params(email='3@qq.com').all()
print(type(res[0])) # 是book的对象，但是查的是User表 不要这样写
print(res[0].name) #
# 8 高级查询
# 条件
# 表达式，and条件连接
res = session.query(User).filter(User.id > 1, User.name == 'lqz099').all() # and条件
# between
res = session.query(User).filter(User.id.between(1, 9), User.name == 'lqz099').all()
res = session.query(User).filter(User.id.between(1, 9)).all()
# in
res = session.query(User).filter(User.id.in_([1,3,4])).all()
res = session.query(User).filter(User.email.in_(['3@qq.com','r@qq.com'])).all()
# ~非，除..外
res = session.query(User).filter(~User.id.in_([1,3,4])).all()
print(res)
# 二次筛选
res = session.query(User).filter(~User.id.in_(session.query(User.id).filter_by(name='lqz'))).all()
print(res)
# and or条件
from sqlalchemy import and_, or_
# or_包裹的都是or条件，and_包裹的都是and条件
res = session.query(User).filter(and_(User.id >= 3, User.name == 'lqz099')).all() # and条件
res = session.query(User).filter(User.id < 3, User.name == 'lqz099').all() # 等同于上面
res = session.query(User).filter(or_(User.id < 2, User.name == 'eric')).all()
res = session.query(User).filter(or_(User.id < 2,and_(User.name == 'lqz099', User.id > 3),User.extra != ""))
# 通配符，模糊查询，以e开头，不以e开头
res = session.query(User).filter(User.email.like('%@%')).all()
# select user.id from user where user.name not like e%;
res = session.query(User.id).filter(~User.name.like('e%'))
res = session.query(User).filter(~User.name.like('e%')).all()
# 分页
# 一页2条，查第5页
res = session.query(User)[2*5:2*5+2]
# 排序，根据name降序排列（从大到小）
res = session.query(User).order_by(User.email.desc()).all()
res = session.query(Book).order_by(Book.price.desc()).all()
res = session.query(Book).order_by(Book.price.asc()).all()
# 第一个条件重复后，再按第二个条件升序排
res = session.query(User).order_by(User.name.desc(), User.id.asc())
# 分组查询 5个聚合函数
from sqlalchemy.sql import func
# 分组后，只能拿分组字段和聚合函数字典，如果拿别的，是严格模式，会报错
res = session.query(User).group_by(User.extra) # 如果是严格模式，就报错
# 分组之后取最大id，id之和，最小id 和分组的字段
# 5个聚合函数(最大、最小、平均、求和、计数)
from sqlalchemy.sql import func
res = session.query(
User.name,
func.max(User.id),
func.sum(User.id),
func.min(User.id),
func.avg(User.id)).group_by(User.name).all()
for item in res:
print(item)
# 分组后筛选：having
# select name,max(id),sum(id),min(id) from user group by user.name having id_max>2;
from sqlalchemy.sql import func
res = session.query(
User.name,
func.max(User.id),
func.sum(User.id),
func.min(User.id)).group_by(User.name).having(func.max(User.id) > 2).all()
print(res)
八 连表查询
### 关联关系，基于连表的跨表查询
from models1 import Person,Hobby
# 连表操作
select * from person,hobby where person.hobby_id=hobby.id;
res = session.query(Person, Hobby).filter(Person.hobby_id == Hobby.id).all()
# 自己连表查询
# join表，默认是inner join,自动按外键关联
# select * from Person inner join Hobby on Person.hobby_id=Hobby.id;
# res = session.query(Person).join(Hobby).all()
#isouter=True 外连，表示Person left join Favor，没有右连接，反过来即可
# select * from Person left join Hobby on Person.hobby_id=Hobby.id;
# res = session.query(Person).join(Hobby, isouter=True).all()
# 没有right join，通过这个实现
# res = session.query(Hobby).join(Person, isouter=True).all()
# # 自己指定on条件（连表条件）,第二个参数，支持on多个条件，用and_,同上
# select * from Person left join Hobby on Person.id=Hobby.id;
# res = session.query(Person).join(Hobby, Person.hobby_id == Hobby.id, isouter=True) # sql本身有问题，只是给你讲， 自己指定链接字段
# 右链接
# print(res)
# 多对多关系连表
# 多对多关系，基于链表的跨表查
# 多表链接
#方式一：直接连
#select * FROM boy, girl, boy2girl WHERE boy.id = boy2girl.boy_id AND girl.id = boy2girl.girl_id
# res = session.query(Boy, Girl,Boy2Girl).filter(Boy.id == Boy2Girl.boy_id,Girl.id == Boy2Girl.girl_id)
# 方式二：join连
# SELECT* FROM boy INNER JOIN boy2girl ON boy.id = boy2girl.boy_id INNER JOIN girl ON girl.id = boy2girl.girl_id WHERE boy.id >= %(id_1)s
res = session.query(Boy).join(Boy2Girl).join(Girl).filter(Boy.id>=2)
print(res)
九 原生sql(django-orm如何执行原生sql)
9.1 sqlalchemy执行原生sql
# 有的复杂sql 用orm写不出来--->用原生sql查询
# 原生sql查询，查出的结果是对象
# 原生sql查询，查询结果列表套元组
from sqlalchemy.orm import sessionmaker, relationship
from sqlalchemy import create_engine
engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/db001", max_overflow=0, pool_size=5)
Session = sessionmaker(bind=engine)
session = Session()
#### 执行原生sql方式一：
# 查询：
# cursor = session.execute('select * from users')
# result = cursor.fetchall()
# print(result) #列表套元组
# 添加
# cursor = session.execute('insert into users(name,email) values(:name,:email)',
# params={"name": 'lqz', 'email': '3333@qq.com'})
# session.commit()
# print(cursor.lastrowid)
###执行原生sql方式二（以后都用session操作--->socpe_session线程安全）一般不用
# conn = engine.raw_connection()
# cursor = conn.cursor()
# cursor.execute(
# "select * from app01_book"
# )
# result = cursor.fetchall()
# 执行原生sql方式三：结果是对象
# res = session.query(User).from_statement(text("SELECT * FROM boy where name=:name")).params(name='lqz').all()
session.close()
9.2 django执行原生sql
# 执行完的结果映射到对象中--->上面讲的 方式三：
from model import Book
books_obj_list = Book.objects.raw('select distinct id, book_name from test_book')
for book_obj in books_obj_list:
print(book_obj.id, book_obj.book_name)
# 纯原生sql
from django.db import connection
cur=connection.cursor()
cur.execute('select distinct id, book_name from test_book')
print(cur.fetch_all())
cur.close()
with connection.cursor() as cur:
cur.execute('select distinct id, book_name from test_book')
十 flask-sqlalchemy使用
10.1 sqlalchemy自己操作
目录结构
-src
-__init__.py
-models.py
-session_sql.py
-settings.py
-views.py
-manage.py
src/init.py
from flask import Flask
app = Flask(__name__)
app.config.from_pyfile('settings.py')
from .views import user
app.register_blueprint(user)
src/models.py
from sqlalchemy import Column, Integer, String, Text, ForeignKey, DateTime, UniqueConstraint, Index
from sqlalchemy.ext.declarative import declarative_base
import datetime
from sqlalchemy.orm import relationship
Base = declarative_base()
# print(type(Base))
class User(Base):
# 以__开头的是配置
__tablename__ = 'users' # 数据库表名称，如果不写，以类名作为表名
id = Column(Integer, primary_key=True) # 主键索引，聚簇索引
name = Column(String(64), index=True, nullable=False) # name字段加辅助索引
email = Column(String(32), unique=True)
# datetime.datetime.now不能加括号，加了括号，以后永远是当前时间
ctime = Column(DateTime, default=datetime.datetime.now)
extra = Column(Text, nullable=True)
__table_args__ = (
UniqueConstraint('id', 'name', name='uix_id_name'), # 联合唯一
Index('ix_id_name', 'name', 'email'), # 索引
)
def __str__(self):
return self.name
def __repr__(self):
return self.name
class Hobby(Base):
__tablename__ = 'hobby'
id = Column(Integer, primary_key=True)
caption = Column(String(50), default='篮球')
def __str__(self):
return self.caption
def __repr__(self):
return self.caption
class Person(Base):
__tablename__ = 'person'
id = Column(Integer, primary_key=True) # 不会自动生成id
name = Column(String(32), index=True, nullable=True)
# hobby指的是tablename而不是类名
# 一对多关系一旦确立，关联关系写在多的一方---》物理外键
hobby_id = Column(Integer, ForeignKey("hobby.id"))
# 跟数据库无关，不会新增字段，只用于快速链表操作
# 类名，backref用于反向查询
hobby = relationship('Hobby', backref='pers') # 以后 person.hobby 就是hobby对象
def __str__(self):
return self.name
def __repr__(self):
return self.name
# 多对多关系
# 中间表 手动创建
class Boy2Girl(Base):
__tablename__ = 'boy2girl'
id = Column(Integer, primary_key=True, autoincrement=True)
girl_id = Column(Integer, ForeignKey('girl.id'))
boy_id = Column(Integer, ForeignKey('boy.id'))
class Girl(Base):
__tablename__ = 'girl'
id = Column(Integer, primary_key=True)
name = Column(String(64), unique=True, nullable=False)
def __str__(self):
return self.name
def __repr__(self):
return self.name
class Boy(Base):
__tablename__ = 'boy'
id = Column(Integer, primary_key=True, autoincrement=True) #autoincrement 默认就是true
name = Column(String(64), unique=True, nullable=False)
# 就是咱们之前的ManyToMany，不会在表中生成字段---》因为它是个表----》这个字段可以放在Girl表
girls = relationship('Girl', secondary='boy2girl', backref='boys')
def __str__(self):
return self.name
def __repr__(self):
return self.name
src/session_sql.py
from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker
from sqlalchemy.orm import scoped_session
from . import app
# engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/db001")
engine = create_engine(app.config['DB_URL'])
Session = sessionmaker(bind=engine)
session = scoped_session(Session)
src/settings.py
DEBUG=True
DB_URL='mysql+pymysql://root:123@127.0.0.1:3306/db001'
src/views.py
from flask import Blueprint
from .models import User
user = Blueprint('user', __name__)
from .session_sql import session
@user.route('/')
def index():
# 查询数据
res = session.query(User).filter_by(name='lqz').all()
print(res)
return 'asdfasdf'
manage.py
from src import app
if __name__ == '__main__':
app.run()
10.2 使用flask-sqlalchemy
# sqlalchemy 集成到flask中
# 第三方: flask-sqlalchemy 封装了用起来，更简洁
# 使用flask-sqlalchemy集成
1 导入 from flask_sqlalchemy import SQLAlchemy
2 实例化得到对象
db = SQLAlchemy()
3 将db注册到app中
db.init_app(app)
4 视图函数中使用session
全局的db.session # 线程安全的
5 models.py 中继承Model
db.Model
6 写字段
username = db.Column(db.String(80), unique=True, nullable=False)
7 配置文件中加入
SQLALCHEMY_DATABASE_URI = "mysql+pymysql://root@127.0.0.1:3306/ddd?charset=utf8"
SQLALCHEMY_POOL_SIZE = 5
SQLALCHEMY_POOL_TIMEOUT = 30
SQLALCHEMY_POOL_RECYCLE = -1
# 追踪对象的修改并且发送信号
SQLALCHEMY_TRACK_MODIFICATIONS = False
init.py文件
from flask import Flask
# 第一步：导入
from flask_sqlalchemy import SQLAlchemy
app = Flask(__name__)
# 第二步：实例化得到对象
db = SQLAlchemy()
app.config.from_pyfile('settings.py')
# 第三步：注册到app中
db.init_app(app)
from .views import user
app.register_blueprint(user)
models.py
# 第四步：在models中，找所有东西 都从db中拿
from src import db
class User(db.Model):
# 以__开头的是配置
__tablename__ = 'users' # 数据库表名称，如果不写，以类名作为表名
id = db.Column(db.Integer, primary_key=True) # 主键索引，聚簇索引
name = db.Column(db.String(64), index=True, nullable=False) # name字段加辅助索引
email = db.Column(db.String(32), unique=True)
__table_args__ = (
db.UniqueConstraint('id', 'name', name='uix_id_name'), # 联合唯一
db.Index('ix_id_name', 'name', 'email'), # 索引
)
def __str__(self):
return self.name
def __repr__(self):
return self.name
views.py
from flask import Blueprint
from .models import User
user = Blueprint('user', __name__)
from src import db
@user.route('/')
def index():
res = db.session.query(User).filter_by(name='lqz').all()
print(res)
return 'asdfasdf'
settings.py
DEBUG=True
SQLALCHEMY_DATABASE_URI = "mysql+pymysql://root:123@127.0.0.1:3306/db001?charset=utf8"
SQLALCHEMY_POOL_SIZE = 5
SQLALCHEMY_POOL_TIMEOUT = 30
SQLALCHEMY_POOL_RECYCLE = -1
# 追踪对象的修改并且发送信号
SQLALCHEMY_TRACK_MODIFICATIONS = False
