Based outside migration framework
1 demo_class = g.db.query (Model) .get (id)
2 equal 等值
article = session.query(model).filter(model.title=="title").first()
select * from model_table where titile == "title"
3 not equal value ranging
article = session.query(model).filter(model.title != "title").first()
4 in not in
articles = session.query(model).filter(model.title.in_(["one", "two"]))
articles = session.query(model).filter(~model.title.in_(["there", "four"])
5 is null
articles = session.query(model).filter(model.count==none).all()
6 is not null
artiles = session.query(model).filter(model.count !=none).all()
7 from sqlalchemy import and_,or_
# and
# articles = session.query(Article).filter(Article.title=='abc',Article.content=='abc').all()
# print(articles)
# or
articles = session.query(Article).filter(or_(Article.title=='abc',Article.content=='abc')).all()
print(articles)
If you want to see the sql statement orm underlying the conversion, you can not to execute any of the methods behind the filter method, we can see the direct printing.
Plainly it is to execute the statement added only filter without actuator
比如：
```python
articles = session.query(Article).filter(or_(Article.title=='abc',Article.content=='abc'))
print(articles)
```
There are configuration items in sqlalchemy the output sql statement directly in the print station
SQLALCHEMY_ECHO = True
Using foreign keys
ForeignKey a foreign key relationship between this ratio is relatively simple and clear, and to ensure that the parent table field associated foreign key of the primary key field is consistent but not enough examples ORM
This method does not use long queries more strenuous
class User(Base):
__tablename__ = 'user'
id = Column(Integer,primary_key=True,autoincrement=True)
username = Column(String(50),nullable=False)
class Article(Base):
__tablename__ = 'article'
id = Column(Integer,primary_key=True,autoincrement=True)
title = Column(String(50),nullable=False)
content = Column(Text,nullable=False)
uid = Column(Integer,ForeignKey("user.id"))
usre = session.query(User).filter(User.username =="查询").first()
user = session.query(Article).filter(Article.uid==user.id).all()
2 . SQLAlchemy provides a `relationship`, the class attributes may be defined, later when accessing the table directly associated attributes can be accessed through access can be obtained
class Wuye(Base):
__tablename__ = 'user'
id = Column(Integer,primary_key=True,autoincrement=True)
wuye_name = Column(String(50),nullable=False)
# uptown= relationship("Uptown")
class Uptown(Base):
__tablename__ = 'article'
id = Column(Integer,primary_key=True,autoincrement=True)
title = Column(String(50),nullable=False)
content = Column(Text,nullable=False)
wuye_id = Column(Integer,ForeignKey("user.id"))
Wuye = relationship("Wuye",backref="uptown")
backref reverse attribute is to add a field uptown uptown in the table is a plurality Wuye many relationship
Using foreign keys
Get the current query all cells of the small property-many and many-to a query
uptown = session.query (Uptown) .filter (Uptown.wuye_id == current property id) .all ()
wuye = session.query (Wuye) .filter (Wuye.status == 0) .first ()
uptown = wuye.uptown[0].id
Underlying query
pass
Inquire
En join
In this way the number of cells and the presence of link property belonging to the same acquisition
uptown = session.qyery(Uptown).filter(Uptown.wuye_id ==Wuye.id).coun()
uptown = session(UptownModel).join(WuyeModel, UptownModel.wuye_id==WuyeModel.id).count()
Links within the default by a foreign key query
# FROM (SELECT uptown.id AS uptown_id, uptown.uptown_name AS uptown_uptown_name
# FROM uptown, wuye
# WHERE uptown.wuye_id = wuye.id) AS anon_
Outer join
outerjoin LEFT OUTER JOIN wuye ON cell to be mainly associated with the query does not exist property is null
FROM (SELECT uptown.id AS uptown_id, uptown.uptown_name AS uptown_uptown_name
FROM uptown LEFT OUTER JOIN wuye ON uptown.wuye_id = wuye.id) AS anon_1
In a subquery select statement, the select statement embedded in another, then the select statement called embedded subquery
subquery () simply understood word query result is the query as a query to another query conditions
Queries district exist property
wuye_id = g.db.query(WuyeModel.id).filter(WuyeModel.status==0).subquery()
uptown = g.db.query(UptownModel).filter(UptownModel.status==0, UptownModel.wuye_id.in_(wuye_id)).all()
Check for phrases
FROM uptown
WHERE uptown.status = %(status_1)s AND uptown.wuye_id IN (SELECT wuye.id
FROM wuye
WHERE wuye.status = %(status_2)s