[flask] crud addition and query operation of data

use session Add, delete, modify and query data ：

1、 Create model classes , Generate data table

# First step ： Create base class 
Base=declarative_base(engine)

# The second step ： Definition python Mapping of classes and tables 
class Person(Base):
    __tablename__='t_person'  # Create table name , It is best to t_ start 
    id=Column(name='id',type_=Integer,primary_key=True,autoincrement=True)
    name=Column(name='name',type_=String(255))
    age=Column(name='age',type_=Integer)
    address=Column(name='address',type_=String(255))
    country=Column(name='country',type_=String(50))  # New fields added after the table is created 
    city=Column(name='city',type_=String(50))        # New fields added after the table is created 

     def __str__(self):
        return ' full name :{}- Annual collar :{}- Address :{}- Country :{}- City :{}'.format(self.name,self.age,self.address,self.country,self.city)


# The third step ： Model classes create tables 
#Base.metadata.drop_all()
Base.metadata.create_all()

2、 structure session object ：

All and database ORM All operations must pass through a process called session To implement ,
Get the session object through the following code ：

from sqlalchemy.orm import sessionmaker
engine = create_engine(DB_URI)
Base = declarative_base(engine)
session = sessionmaker(engine)() #  Be careful , Returns a function 

Particular attention 1：session = sessionmaker(engine)() Returns a function

3、 Add data （C）

Add a piece of data

# Create objects , That is, create a piece of data ：
p1=Person(name='zz',age=20,address=' Fengtai District ',country=' China ',city=' Beijing ')
#  Add this object to `session` In the session object ：
session.add(p1)
#  take session The objects in do commit operation （ Submit ）
session.commit()

Add multiple pieces of data at one time

# Add data to database 
p1=Person(name='django',age=17,address=' Fengtai District ',country=' China ',city=' Beijing ')
p2=Person(name='kb',age=21,address=' Daxing District ',country=' China ',city=' Beijing ')
p3=Person(name='python',age=18,address=' Changping District ',country=' China ',city=' Beijing ')
p4=Person(name='flask',age=25,address=' Haidian District ',country=' China ',city=' Beijing ')
session.add_all([p1,p2,p3,p4])
session.commit()

4、 Find data

1、 Find all the data in the table corresponding to the model

all_person=session.query(Person).all()
for person in all_person:
    print(person)

 full name :zz- Annual collar :20- Address : Fengtai District - Country : China - City : Beijing 
 full name :django- Annual collar :17- Address : Fengtai District - Country : China - City : Beijing 
 full name :kb- Annual collar :21- Address : Daxing District - Country : China - City : Beijing 
 full name :python- Annual collar :18- Address : Changping District - Country : China - City : Beijing 
 full name :flask- Annual collar :25- Address : Haidian District - Country : China - City : Beijing 

2、 Use first Method to get the first data in the result set

p1=session.query(Person).first()
print(p1)

 full name :zz- Annual collar :20- Address : Fengtai District - Country : China - City : Beijing 

3、 Use filter To do condition query
for example ： The inquiry year is 20 People over years old

p2=session.query(Person).filter(Person.age>20)
print(p2)

Print the results ： It's a piece. sql sentence

SELECT t_person.id AS t_person_id, t_person.name AS t_person_name, t_person.age AS t_person_age, t_person.address AS t_person_address, t_person.country AS t_person_country, t_person.city AS t_person_city 
FROM t_person 
WHERE t_person.age > %(age_1)s

Be careful 2： Just add first,all Function will return specific data , Otherwise, only print out sql sentence

p3=session.query(Person).filter(Person.age>20).all()
for p in p3:
    print(p)

 full name :kb- Annual collar :21- Address : Daxing District - Country : China - City : Beijing 
 full name :flask- Annual collar :25- Address : Haidian District - Country : China - City : Beijing 

4、 Use filter_by To do condition query

p4=session.query(Person).filter_by(age=20).all()
for p in p4:
   print(p)

 full name :zz- Annual collar :20- Address : Fengtai District - Country : China - City : Beijing 

5、 ... and 、filter Filter conditions ：

Filtering is a very important function of data extraction , Here are some common filter conditions to explain , And these filter conditions can only pass through filter Method ：
Particular attention 3：filter: Use model class name . Property name ==' Property value ’ Filter queries

1.equals ：

Query name python Your character information

p5=session.query(Person).filter(Person.name=='python').all()
print(p5)

2.not equals : !

The query name is not flask Your character information

p6=session.query(Person).filter(Person.name!='flask').all()
print(p6)

3.like & ilike [ Case insensitive ]：

The query name contains an Your character information

p7=session.query(Person).filter(Person.name.like('%an%')).all()
print(p7)

4. in_：

The query area is the person information under Haidian District and Changping District

p8=session.query(Person).filter(Person.address.in_([' Changping District ',' Haidian District '])).all()
print(p8)

5. not in：

The query area is not the task information under Haidian District and Changping District

p9=session.query(Person).filter(~Person.address.in_([' Changping District ',' Haidian District '])).all()
print(p9)

6. is null：

The query annual income is None Your character information

p10=session.query(Person).filter(Person.age==None).all()
print(p10)
 perhaps 
p11=session.query(Person).filter(Person.age.is_(None)).all()
print(p11)

7. is not null:

The query annual income is not None Your character information

p12=session.query(Person).filter(Person.age!=None).all()
print(p12)
p13=session.query(Person).filter(Person.age.isnot(None)).all()
print(p13)

8. and_：

The search name is python, And the annual income is 20 Year old character information

p14=session.query(Person).filter(Person.name=='python',Person.age=='20').all()
print(p14)
 perhaps 
p15 = session.query(Person).filter(and_(Person.name == 'python', Person.age == '20')).all()
print(p15)
 perhaps 
p16= session.query(Person).filter(Person.name == 'python').filter(Person.age=='20').all()
print(p16)

9. or_：

The search name is python, Or the annual income is 18 Year old character information

p17=session.query(Person).filter(or_(Person.name=='python',Person.age=='20')).all()
print(p17)

Particular attention 4： above and_、or_ All need to import

from sqlalchemy import and_,or_