sqlalchemy 笔记

初始化数据库连接

DB_CONNECT_STRING = 'mysql+mysqldb://root:123123@localhost/sqlalchemy?charset=utf8'
engine = create_engine(DB_CONNECT_STRING, echo=True)

数据库类型+数据库驱动名称://用户名:口令@机器地址:端口号/数据库名

创建DBSession

DB_Session = sessionmaker(bind=engine)
session = DB_Session()

执行 SQL

session.execute('create database abc') print session.execute('show databases').fetchall() session.execute('use mysql') #查询所有 print session.execute('select * from user').fetchall(), "fetchall" #第一条 print session.execute('select * from user').first(), "first" #第一条 print session.execute('select * from user').fetchone(), "fetchone" #查询2条记录 print session.execute('select * from user').fetchmany(2), "fetchmany"

Model

#declarative_base() 创建了一个 BaseModel 类，这个类的子类可以自动与一个表关联。
BaseModel = declarative_base()
class User(BaseModel):
    # 表的名字:
    __tablename__ = 'user'

    # 表的结构:
    id = Column(Integer, primary_key=True)
    name = Column(String(20), nullable=False, unique=True)
    test = Column(String(20), name="a1", default="a1")
    email_address = Column(String(32), nullable=False, default="email")

    def __repr__(self):
        return '<User id=%s,name=%s,test=%s,email_address=%s >' % (self.id, self.name, self.test, self.email_address)

primary_key 主键，自增
unique 唯一 UNIQUE (name)
name 数据库字段名字
nullable 是否可以为空 False NOT NULL
default 默认值

表属性

class User(BaseModel):
    __table_args__ = {
        'mysql_engine': 'InnoDB',
        'mysql_charset': 'utf8'
    }

建表 or 删除表

#建表
User.metadata.create_all(engine) or  BaseModel.metadata.create_all(engine) #创建所有BaseModel的之类的表
#删除表
User.metadata.drop_all(engine) or BaseModel.metadata.drop_all(engine) #同上

使用

u1 = User(name="aa", email_address="aa_email")
u2 = User(name="bb")
session.add(u1)
session.add(u2)
session.commit()#提交会话 query = session.query(User) for user in query: print user print query.all() # 查询所有 print query.offset(1).limit(2).all() # LIMIT 1, 2 print query.first() # 第一条,不存在返回None # print query.one() #之获取一条，不存在，或有多行记录时会抛出异常 print query.filter(User.id == 2).all() # WHERE "user".id = 2 print query.filter(User.id >= 1).all() # WHERE "user".id >= 1 print query.filter(User.id == User.name).all() # WHERE user.id = user.name print query.filter(User.id >= 1).filter(User.id <= 11).all() # WHERE "user".id >= 1 AND user.id <= 11 print query.filter(User.id >= 1, User.id <= 11).all() # 同上 print query.filter(or_(User.id >= 1, User.id <= 11), User.name == "111").all() # (user.id >= 1 OR user.id <=11) AND user.name = 111 print query.filter(User.id.in_((1, 2))).all() # user.id IN (1, 2) print query.filter(User.name.like("a")).all() # user.name LIKE "a" print query.filter(User.name.isnot(None)).all() # WHERE user.name IS NOT NULL print query.filter(User.name != None).all() # WHERE user.name IS NOT NULL print query.filter(not_(User.id != 1), not_(User.name.like("a"))).all() # WHERE user.id = 1 AND user.name NOT LIKE a print query.filter("id is null").all() # 支持字符串 print query.get(2) # 以主键获取,WHERE "user".id = 2 print query.order_by("name") # ORDER BY "user".name print query.order_by(User.name) # 同上 print query.order_by(User.name.desc()) # ORDER BY "user".name desc # print query.order_by("name desc")# 同上 print query.order_by(User.name.desc(), User.id.desc()) # ORDER BY name desc, id desc print query.count() print "#" * 30 #修改 # query.filter(User.id == 1).update({User.name: 'c'}) print "#" * 30 query2 = session.query(User).order_by(User.name.desc(), User.id.desc()) print query2.all() print "#" * 30 # 返回元组 query3 = session.query(User.name) print query3.all() print query3.filter(User.id == 1).scalar() # 如果有记录，返回第一条记录的第一个元素 print session.query('id', "name").select_from(User).filter( User.id == 1).scalar() # SELECT id, name FROM user WHERE user.id = 1 print "#" * 30 print session.query(func.count('1')).select_from(User).scalar() print session.query(User).filter(User.name == func.now())#WHERE "user".name = now() print session.query(func.count(User.id)).select_from(User).scalar() print session.query(func.sum(User.id)).select_from(User).scalar() print session.query(func.now()).scalar() # func 后可以跟任意函数名，只要该数据库支持 print session.query(User.id, func.md5(User.name)).filter(User.id == 1).all() u = session.query(User).get(1) print u u.name = "1111111111" session.flush()# 写数据库，但并不提交 print session.query(User).get(1) session.rollback()#返回 print session.query(User).get(1) u.name = "1111111111" print query.all() #优先操作 HIGH_PRIORITY 滞后操作 LOW_PRIORITY 延时插入 INSERT DELAYED session.query(User.name).prefix_with('HIGH_PRIORITY').all()#SELECT HIGH_PRIORITY user.name AS user_name FROM user print query.all() # session.delete(session.query(User).get(2)) # session.delete(session.query(User).first()) # session.query(User).filter(User.id >= 1).delete() session.commit() 

外建

class User(BaseModel):
    # 表的名字:
    __tablename__ = 'user'

    # 表的结构:
    id = Column(Integer, primary_key=True)
    name = Column(String(20), nullable=False, unique=True)
    test = Column(String(20), name="a1", default="a1")
    email_address = Column(String(32), nullable=False, default="email")
    addresses = relationship("Address", order_by="Address.id", backref="user")

    def __repr__(self):
        return '<User id=%s,name=%s,test=%s,email_address=%s >' % (self.id, self.name, self.test, self.email_address)


class Address(BaseModel):
    __tablename__ = 'address'

    id = Column(Integer, primary_key=True)
    address = Column(String(20), nullable=False, unique=True)
    user_id = Column(Integer, ForeignKey('user.id', ondelete='CASCADE', onupdate='CASCADE'))

    def __repr__(self):
        return '<User id=%s,name=%s,test=%s,email_address=%s >' % (self.id, self.address)

user_id = Column(Integer, ForeignKey(‘user.id’, ondelete=’CASCADE’, onupdate=’CASCADE’)) 原因是删除 user 表的数据，可能会导致 address 的外键不指向一个真实存在的记录。在默认情况下，MySQL 会拒绝这种操作，也就是 RESTRICT。InnoDB 还允许指定 ON DELETE 为 CASCADE 和 SET NULL，前者会删除 friendship 中无效的记录，后者会将这些记录的外键设为 NULL。
relationship 标记User的addresses连接到Address表，session.query(User).filter(User.name == “bb”).one().addresses
backref 反向查询的细节 session.query(Address).filter(Address.address==”a1”).one().user

u1 = User(name="aa", email_address="aa_email")
u2 = User(name="bb")

a1 = Address(address="a1")
a2 = Address(address="a2")
a3 = Address(address="a3")

u2.addresses = [a1, a2]
session.add(u1)
session.add(u2)
session.add(a3)
session.flush()

session.commit()
print session.query(User).filter(User.name == "bb").one().addresses
print session.query(Address).filter(Address.address=="a1").one().user

print session.query(User).all()
print session.query(Address).all()

多对多

user_keywords = Table('user_keywords',
                      BaseModel.metadata,
                      Column('user_id', Integer, ForeignKey('user.id')),
                      Column('keyword_id', Integer, ForeignKey('keyword.id'))
                      )

class User(BaseModel):
    # 表的名字:
    __tablename__ = 'user'

    # 表的结构:
    id = Column(Integer, primary_key=True)
    name = Column(String(20), nullable=False, unique=True)
    test = Column(String(20), name="a1", default="a1")
    email_address = Column(String(32), nullable=False, default="email")
    keywords = relation("Keyword", secondary=user_keywords, backref="user")

    def __repr__(self):
        return '<User id=%s,name=%s,test=%s,email_address=%s >' % (self.id, self.name, self.test, self.email_address)

class Keyword(BaseModel):
    __tablename__ = 'keyword'

    id = Column(Integer, primary_key=True)
    keyword = Column(String(20), nullable=False, unique=True)
    user = relation("User", secondary=user_keywords, backref="user")

    def __repr__(self):
        return '<User id=%s,keyword=%s>' % (self.id, self.keyword)