day63
参考：http://www.cnblogs.com/wupeiqi/articles/5713330.html
SQLAlchemy本身无法操作数据库，其必须以来pymsql等第三方插件，Dialect用于和数据API进行交流，根据配置文件的不同调用不同的数据库API，从而实现对数据库的操作，如：
MySQL-Python mysql+mysqldb://<user>:<password>@<host>[:<port>]/<dbname> pymysql mysql+pymysql://<username>:<password>@<host>/<dbname>[?<options>] MySQL-Connector mysql+mysqlconnector://<user>:<password>@<host>[:<port>]/<dbname> cx_Oracle oracle+cx_oracle://user:pass@host:port/dbname[?key=value&key=value...] 更多详见：http://docs.sqlalchemy.org/en/latest/dialects/index.html |
可以连接不同的数据库。
1. ORM框架：SQLAlchemy
- 作用：
1. 提供简单的规则
2. 自动转换成SQL语句
- DB first: 手动创建数据库以及表 -> ORM框架 -> 自动生成类
- code first： 手动创建类、和数据库 -> ORM框架 -> 以及表
a. 功能
- 创建数据库表
- 连接数据库（非SQLAlchemy,pymyql,mysqldb,....）
- 类转换SQL语句
- 操作数据行
增
删
改
查
- 便利的功能
1 from sqlalchemy.ext.declarative import declarative_base
2 from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index
3 from sqlalchemy.orm import sessionmaker, relationship
4 from sqlalchemy import create_engine
5
6
7
8 Base = declarative_base()
9 class UsersType(Base):#必须继承base
10 __tablename__ = 'usertype'#表名 #自增
11 id = Column(Integer, primary_key=True, autoincrement=True)#生成三列 Column
12 title = Column(String(32), nullable=True, index=True)#建立索引
13
14 # 创建单表
15 class Users(Base):#必须继承base
16 __tablename__ = 'users'#表名 #自增
17 id = Column(Integer, primary_key=True, autoincrement=True)#生成三列 Column
18 name = Column(String(32), nullable=True, default='sf', index=True)#建立索引
19 extra = Column(String(16), unique=True)#唯一索引
20
21 user_type_id = Column(Integer, ForeignKey("usertype.id"))#建立外键 user_type_id对应usertype中的id
22
23 __table_args__ = (
24 UniqueConstraint('id', 'name', name='uix_id_name'), #联合唯一索引
25 Index('ix_id_name', 'name', 'extra'), #普通索引
26 )
27
28 #连远程 127.0.0.1本机 配置 #最多5个连接
29 engine = create_engine("mysql+pymysql://root:112358@127.0.0.1:3306/nzp?charset=utf8", max_overflow = 5)
30 Base.metadata.create_all(engine)
实现增、删、改、查
1 from sqlalchemy.ext.declarative import declarative_base
2 from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index
3 from sqlalchemy.orm import sessionmaker, relationship
4 from sqlalchemy import create_engine
5
6
7
8 Base = declarative_base()
9
10 class UsersType(Base):#必须继承base
11 __tablename__ = 'usertype'#表名 #自增
12 id = Column(Integer, primary_key=True, autoincrement=True)#生成三列 Column
13 title = Column(String(32), nullable=True, index=True)#建立索引
14
15 # 创建单表
16 class Users(Base):#必须继承base
17 __tablename__ = 'users'#表名 #自增
18 id = Column(Integer, primary_key=True, autoincrement=True)#生成三列 Column
19 name = Column(String(32), nullable=True, default='sf', index=True)#建立索引
20 extra = Column(String(16), unique=True)#唯一索引
21
22 user_type_id = Column(Integer, ForeignKey("usertype.id"))#建立外键
23
24 __table_args__ = (
25 UniqueConstraint('id', 'name', name='uix_id_name'), #联合唯一索引
26 Index('ix_id_name', 'name', 'extra'),#普通索引
27 )
28
29 # #连远程 127.0.0.1本机 配置 #最多5个连接
30 # engine = create_engine("mysql+pymysql://root:112358@127.0.0.1:3306/nzp?charset=utf8", max_overflow = 5)
31 # Base.metadata.create_all(engine) #创建表
32 # #Base.metadata.drop_all(engine)# 删掉表
33
34 #建表
35 def create_db():
36 engine = create_engine("mysql+pymysql://root:112358@127.0.0.1:3306/nzp?charset=utf8", max_overflow=5)
37 Base.metadata.create_all(engine) # 创建表
38 #删表
39 def drop_db():
40 engine = create_engine("mysql+pymysql://root:112358@127.0.0.1:3306/nzp?charset=utf8", max_overflow=5)
41 Base.metadata.drop_all(engine) # 创建表
42
43
44 engine = create_engine("mysql+pymysql://root:112358@127.0.0.1:3306/nzp?charset=utf8", max_overflow=5)
45 Session = sessionmaker(bind=engine)
46 session = Session()
47
48 # # 增
49 # # 添加一行
50 # # obj1 = UsersType(title="狗剩")#给usertype表添加
51 # # session.add(obj1)
52 # '''添加多行数据'''
53 # objs = [
54 # UsersType(title='tghh'),
55 # UsersType(title='sdcs'),
56 # UsersType(title='cbsu'),
57 # ]
58 # session.add_all(objs)
59 # session.commit()
60
61 # #查
62 # user_type_list = session.query(UsersType).all()#其中每一个元素是UserType类型，每一个对象是一行数据
63 # print(type(user_type_list[0])) #row是UsersType类对象 ，类代指表
64 # for row in user_type_list:
65 # print(row.id, row.title)
66
67 # #查部分 #相当于映射 #相当于where
68 # user_type_list = session.query(UsersType.id, UsersType.title).filter(UsersType.id > 2)#其中每一个元素是UserType类型，每一个对象是一行数据
69 # for row in user_type_list:
70 # print(row.id, row.title)
71
72 # #删
73 # session.query(UsersType.id, UsersType.title).filter(UsersType.id > 2).delete()
74 # session.commit()
75
76 #改
77 #session.query(UsersType.id, UsersType.title).filter(UsersType.id > 0).update({'title':"nizhipeng"})#批量更改
78 #session.query(UsersType.id, UsersType.title).filter(UsersType.id > 0).update({UsersType.title: UsersType.title+"x"}, synchronize_session=False)
79 session.query(UsersType.id, UsersType.title).filter(UsersType.id > 0).update({"title": UsersType.id + 1}, synchronize_session="evaluate")
80 session.commit()#需要确认
81
82
83 session.close()
其他：
1 # 条件
2 #or,and,in,between
3 ret = session.query(Users).filter_by(name='alex').all()
4 ret = session.query(Users).filter(Users.id > 1, Users.name == 'eric').all()
5 ret = session.query(Users).filter(Users.id.between(1, 3), Users.name == 'eric').all()
6 ret = session.query(Users).filter(Users.id.in_([1,3,4])).all()
7 ret = session.query(Users).filter(~Users.id.in_([1,3,4])).all()
8 ret = session.query(Users).filter(Users.id.in_(session.query(Users.id).filter_by(name='eric'))).all()
9 from sqlalchemy import and_, or_
10 ret = session.query(Users).filter(and_(Users.id > 3, Users.name == 'eric')).all()
11 ret = session.query(Users).filter(or_(Users.id < 2, Users.name == 'eric')).all()
12 ret = session.query(Users).filter(
13 or_(
14 Users.id < 2,
15 and_(Users.name == 'eric', Users.id > 3),
16 Users.extra != ""
17 )).all()
18
19
20 # 通配符
21 ret = session.query(Users).filter(Users.name.like('e%')).all()
22 ret = session.query(Users).filter(~Users.name.like('e%')).all()#非
23
24 # 限制
25 ret = session.query(Users)[1:2] #切片limit
26
27 # 排序
28 ret = session.query(Users).order_by(Users.name.desc()).all()
29 ret = session.query(Users).order_by(Users.name.desc(), Users.id.asc()).all()
30
31 # 分组
32 from sqlalchemy.sql import func
33
34 ret = session.query(Users).group_by(Users.extra).all()
35 ret = session.query(
36 func.max(Users.id),
37 func.sum(Users.id),
38 func.min(Users.id)).group_by(Users.name).all()
39
40 ret = session.query(
41 func.max(Users.id),
42 func.sum(Users.id),
43 func.min(Users.id)).group_by(Users.name).having(func.min(Users.id) >2).all()#通过名字分组
44
45 # 连表
46 ret = session.query(Users, Favor).filter(Users.id == Favor.nid).all()
47
48 ret = session.query(Person).join(Favor).all()
49
50 ret = session.query(Person).join(Favor, isouter=True).all() #out join
51
52
53 # 组合
54 q1 = session.query(Users.name).filter(Users.id > 2)
55 q2 = session.query(Favor.caption).filter(Favor.nid < 2)
56 ret = q1.union(q2).all()#上下连接 去重
57
58 q1 = session.query(Users.name).filter(Users.id > 2)
59 q2 = session.query(Favor.caption).filter(Favor.nid < 2)
60 ret = q1.union_all(q2).all() # 不去重
其中连表：
改变左右参数顺序，可设置right join或left join。
1 from sqlalchemy.ext.declarative import declarative_base
2 from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index
3 from sqlalchemy.orm import sessionmaker, relationship
4 from sqlalchemy import create_engine
5
6
7
8 Base = declarative_base()
9
10 class UsersType(Base):#必须继承base
11 __tablename__ = 'usertype'#表名 #自增
12 id = Column(Integer, primary_key=True, autoincrement=True)#生成三列 Column
13 title = Column(String(32), nullable=True, index=True)#建立索引
14
15 # 创建单表
16 class Users(Base):#必须继承base
17 __tablename__ = 'users'#表名 #自增
18 id = Column(Integer, primary_key=True, autoincrement=True)#生成三列 Column
19 name = Column(String(32), nullable=True, default='sf', index=True)#建立索引
20 extra = Column(String(16), unique=True)#唯一索引
21
22 user_type_id = Column(Integer, ForeignKey("usertype.id"))#建立外键
23
24 __table_args__ = (
25 UniqueConstraint('id', 'name', name='uix_id_name'), #联合唯一索引
26 Index('ix_id_name', 'name', 'extra'),#普通索引
27 )
28
29 # #连远程 127.0.0.1本机 配置 #最多5个连接
30 # engine = create_engine("mysql+pymysql://root:112358@127.0.0.1:3306/nzp?charset=utf8", max_overflow = 5)
31 # Base.metadata.create_all(engine) #创建表
32 # #Base.metadata.drop_all(engine)# 删掉表
33
34 #建表
35 def create_db():
36 engine = create_engine("mysql+pymysql://root:112358@127.0.0.1:3306/nzp?charset=utf8", max_overflow=5)
37 Base.metadata.create_all(engine) # 创建表
38 #删表
39 def drop_db():
40 engine = create_engine("mysql+pymysql://root:112358@127.0.0.1:3306/nzp?charset=utf8", max_overflow=5)
41 Base.metadata.drop_all(engine) # 创建表
42
43
44 engine = create_engine("mysql+pymysql://root:112358@127.0.0.1:3306/nzp?charset=utf8", max_overflow=5)
45 Session = sessionmaker(bind=engine)
46 session = Session()
47
48 # #连表
49 # result = session.query(Users).join(UsersType).all()#INNER JOIN usertype ON usertype.id = users.user_type_id
50 # print(result)
51
52
53 # #子查询
54 # #select * from (select * from tb) as B
55 # q1 = session.query(UsersType).filter(UsersType.id > 2).subquery()#子查询 #当做一张表
56 # result = session.query(q1).all()
57 # print(result)
58
59 # #select id, (select id from where user.user_type_id = 1) from xxx;
60 # result = session.query(UsersType.id, session.query(Users).filter(Users.id == 1).subquery()).all()
61 # #UsersType.id 加上 Users的第一行
62 # for row in result:
63 # print(row)
64
65 #select * from users where users.user_type_id = usertype.id;
66 result = session.query(UsersType.id, session.query(Users).filter(Users.user_type_id == UsersType.id).as_scalar())#作为一项
67 #session.query(Users).as_scalar()#作为一项#带括号(SELECT users.id, users.name, users.extra, users.user_type_id FROM users)
68 print(result)
69
70
71 session.close()
以上为连表与子查询。
relationship
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index
from sqlalchemy.orm import sessionmaker, relationship
from sqlalchemy import create_engine
Base = declarative_base()
class UsersType(Base):#必须继承base
__tablename__ = 'usertype'#表名 #自增
id = Column(Integer, primary_key=True, autoincrement=True)#生成三列 Column
title = Column(String(32), nullable=True, index=True)#建立索引
# 创建单表
class Users(Base):#必须继承base
__tablename__ = 'users'#表名 #自增
id = Column(Integer, primary_key=True, autoincrement=True)#生成三列 Column
name = Column(String(32), nullable=True, default='sf', index=True)#建立索引
extra = Column(String(16), unique=True)#唯一索引
user_type_id = Column(Integer, ForeignKey("usertype.id"))#建立外键
__table_args__ = (
UniqueConstraint('id', 'name', name='uix_id_name'), #联合唯一索引
Index('ix_id_name', 'name', 'extra'),#普通索引
)
user_type = relationship('UsersType')
# #连远程 127.0.0.1本机 配置 #最多5个连接
# engine = create_engine("mysql+pymysql://root:112358@127.0.0.1:3306/nzp?charset=utf8", max_overflow = 5)
# Base.metadata.create_all(engine) #创建表
# #Base.metadata.drop_all(engine)# 删掉表
#建表
def create_db():
engine = create_engine("mysql+pymysql://root:112358@127.0.0.1:3306/nzp?charset=utf8", max_overflow=5)
Base.metadata.create_all(engine) # 创建表
#删表
def drop_db():
engine = create_engine("mysql+pymysql://root:112358@127.0.0.1:3306/nzp?charset=utf8", max_overflow=5)
Base.metadata.drop_all(engine) # 创建表
engine = create_engine("mysql+pymysql://root:112358@127.0.0.1:3306/nzp?charset=utf8", max_overflow=5)
Session = sessionmaker(bind=engine)
session = Session()
# 问题1. 获取用户信息以及与其关联的用户类型名称(FK,Relationship=>正向操作)
user_list = session.query(Users)
for row in user_list:
print(row.name, row.id, row.user_type.title)#row.user_type直接在usertype中将对应的title数据找到了
# 问题2. 获取用户类型
type_list = session.query(UsersType)
for row in type_list:
print(row.id, row.title, session.query(Users).filter(Users.user_type_id == row.id).all())
# type_list = session.query(UserType)
# for row in type_list:
# print(row.id,row.title,row.xxoo)
session.close()
也可参考：https://www.jianshu.com/p/9771b0a3e589
来源：https://www.cnblogs.com/112358nizhipeng/p/9985278.html