9、ORM框架------SQLAlchemy（2）

 

 

#条件
from sqlalchemy import and_,or_
res1 = sess.query(UserType).filter(UserType.id > 2,UserType.title=='超级').all()   # filter内用','隔开，表示and关系
res2 = sess.query(UserType).filter(UserType.id.between(1,3)).all()  # between表示范围是[1,3]
res3 = sess.query(UserType).filter(UserType.id.in_([1,4])).all()  # in_表示1,4
res4 = sess.query(UserType).filter(~UserType.id.in_([1,4])).all()  # ~ 表示非即not
res5 = sess.query(UserType).filter(UserType.id.in_(sess.query(UserType.id).filter(UserType.title != '黑金'))) #临时表
res6 = sess.query(UserType).filter(or_(
    UserType.id > 1,
    and_(UserType.id > 2,UserType.title=='白金'), #默认就是and
))

 

#通配符
res7 = sess.query(UserType).filter(UserType.title.like('%金')).all()  # like,%
res8 = sess.query(UserType).filter(~UserType.title.like('_金')).all()  # like,_

 

#限制(分页)
res9 = sess.query(UserType).all()[:2]  #切片

 

#排序
res10 = sess.query(UserType).order_by(UserType.id.desc())
res11 = sess.query(UserType).order_by(UserType.id.desc(),UserType.title.asc())  #id重名，按title排

 

#分组
from sqlalchemy import func
res12 = sess.query(User).group_by(User.usertype_id)
res13 = sess.query(
    func.max(User.id),
    func.min(User.id),
    func.sum(User.id),
    func.avg(User.id),
    func.count(User.id)
).group_by(User.usertype_id).having(func.avg(User.id)==2)       #结果是元组

 

#连表
res14 = sess.query(User,UserType).filter(User.usertype_id==UserType.id).all()
for item in res14:
    print(item[0].id,item[0].name,item[0].usertype_id,item[1].id,item[1].title)
res15 = sess.query(User,UserType).join(UserType,isouter=True)   #left join
print(res15)
for item in res15:
    print(item)

SELECT user.id AS user_id, user.name AS user_name, user.usertype_id AS user_usertype_id, usertype.id AS usertype_id, usertype.title AS usertype_title 
FROM user LEFT OUTER JOIN usertype ON usertype.id = user.usertype_id
(<__main__.User object at 0x000001FC18DCF390>, <__main__.UserType object at 0x000001FC18D9A4A8>)
(<__main__.User object at 0x000001FC18DCF160>, <__main__.UserType object at 0x000001FC18D9A710>)
(<__main__.User object at 0x000001FC18D9AB00>, <__main__.UserType object at 0x000001FC18D9A710>)
(<__main__.User object at 0x000001FC18D9ACC0>, <__main__.UserType object at 0x000001FC18D9A780>)

 

#组合
res7 = sess.query(UserType.id,UserType.title).filter(UserType.title.like('%金'))
res12 = sess.query(User.id,User.name)
ret1 = res7.union_all(res12) #去重
ret2 = res7.union_all(res12) #不去重
for i,j in zip(ret1,ret2):
    print(i,j)

(2, '白金') (2, '白金')
(3, '黑金') (3, '黑金')
(3, 'ddd') (3, 'ddd')
(2, 'eee') (2, 'eee')
(1, 'qqq') (1, 'qqq')
(4, 'rrr') (4, 'rrr')

 

#子查询
s1 = sess.execute('select * from user WHERE id IN (SELECT id FROM usertype WHERE usertype.title != "超级")')
for i in s1:
    print(i)
q1 = sess.query(User.id,User.name,User.usertype_id).filter(User.id.in_(sess.query(UserType.id).filter(UserType.title != '超级')))
for i in q1:
    print(i)

s2 = sess.execute('select * from (SELECT title from usertype) as u')
for i in s2:
    print(i)
q2 = sess.query(UserType.title).subquery()
r2 = sess.query(q2).all()
print(r2)

s3 = sess.execute('select *,(SELECT title from usertype where user.usertype_id=usertype.id) from user')
for i in s3:
    print(i)
q3 = sess.query(
    User.id,
    User.name,
    User.usertype_id,
    sess.query(UserType.title).filter(UserType.id==User.usertype_id).as_scalar()　　#此处不能用subquery()
)
for i in q3:
    print(i)

(1, 'qqq', 2)
(2, 'eee', 1)
(3, 'ddd', 2)

(1, 'qqq', 2)
(2, 'eee', 1)
(3, 'ddd', 2)

('普通',)
('白金',)
('黑金',)
('超级',)

[('普通',), ('白金',), ('黑金',), ('超级',)]

(1, 'qqq', 2, '白金')
(2, 'eee', 1, '普通')
(3, 'ddd', 2, '白金')
(4, 'rrr', 4, '超级')

(1, 'qqq', 2, '白金')
(2, 'eee', 1, '普通')
(3, 'ddd', 2, '白金')
(4, 'rrr', 4, '超级')

 

# relationship

# from sqlalchemy.orm import relationship   先导入relationship
# user_type = relationship('UserType',backref='to_user')
# 在有外键的类中加入自定义字段并使用relationship，第一个参数是外键关联的类名，第二个参数在关联类中也生产一个自定义的字段用于反向操作

#1、查询用户信息及用户类型
q1 = sess.query(User)
for i in q1:
    print(i.id,i.name,i.usertype_id,i.user_type.title)

#2、查询用户类型及对应的用户信息
q2 = sess.query(UserType)
for i in q2:
    print(i.title,i.to_user)

1 qqq 2 白金
2 eee 1 普通
3 ddd 2 白金
4 rrr 4 超级
普通 [<__main__.User object at 0x0000023886E5A630>]
白金 [<__main__.User object at 0x0000023886E5A710>, <__main__.User object at 0x0000023886E5A5C0>]
黑金 []
超级 [<__main__.User object at 0x0000023886E5A0F0>]

 

转载于:https://www.cnblogs.com/lybpy/p/8280926.html