常见的sqlalcemy查询

转自其他博客，另外附上找到一个将sqlalchemy的orm基本用法和增删改查的文章
https://www.cnblogs.com/Keep-Ambition/p/8083387.html

几种常见sqlalchemy查询：

简单查询

print(session.query(User).all())
print(session.query(User.name, User.fullname).all())
print(session.query(User, User.name).all())

带条件查询

print(session.query(User).filter_by(name=‘user1’).all())
print(session.query(User).filter(User.name == “user”).all())
print(session.query(User).filter(User.name.like(“user%”)).all())

多条件查询

print(session.query(User).filter(and_(User.name.like(“user%”), User.fullname.like(“first%”))).all())
print(session.query(User).filter(or_(User.name.like(“user%”), User.password != None)).all())

sql过滤

print(session.query(User).filter(“id>:id”).params(id=1).all())

关联查询

print(session.query(User, Address).filter(User.id == Address.user_id).all())
print(session.query(User).join(User.addresses).all())
print(session.query(User).outerjoin(User.addresses).all())

聚合查询

print(session.query(User.name, func.count(’*’).label(“user_count”)).group_by(User.name).all())
print(session.query(User.name, func.sum(User.id).label(“user_id_sum”)).group_by(User.name).all())

子查询

stmt = session.query(Address.user_id, func.count(’*’).label(“address_count”)).group_by(Address.user_id).subquery()
print(session.query(User, stmt.c.address_count).outerjoin((stmt, User.id == stmt.c.user_id)).order_by(User.id).all())

exists

print(session.query(User).filter(exists().where(Address.user_id == User.id)))
print(session.query(User).filter(User.addresses.any()))

限制返回字段查询

person = session.query(Person.name, Person.created_at,Person.updated_at).filter_by(name=“zhongwei”).order_by(Person.created_at).first()

记录总数查询：

from sqlalchemy import func

#count User records, without
#using a subquery.
session.query(func.count(User.id))

#return count of user “id” grouped
#by “name”
session.query(func.count(User.id)).
group_by(User.name)

from sqlalchemy import distinct
#count distinct “name” values
session.query(func.count(distinct(User.name)))