一、復習詳盡如下：

創建一個test庫
create database test;
授權一個用戶
grant all privileges on *.* to ‘xiang‘@‘%‘ identified by ‘1qaz@WSX‘;
創建表
create table student(id int not null);
查詢
select * from tabel_name where 條件1 and  條件2
增加
insert into table_name (id, name, age, sex, grander) values (1, ‘ling‘, 25, ‘M‘, 99), (2, ‘ajing‘, 45, ‘F‘, 88);
改
update table_name set id=10 where 條件判斷
刪除
delete from table_name  where 條件判斷
drop table table_name

聯合查詢
select a.id, b.name from A a join B b on a.id=b.tid

創建索引
create index idx_庫名_表名_列名1_列名2 (列名1， 列名2)

查看sql是否走索引
explain select * from student where name=‘ling‘

鏈接數據庫
Python2 使用的是MySQLdb
python3 使用的pymysql  pip安裝

1. 創建鏈接和遊標
註意：在mysql連接中，盡量使用一個連接，確保mysql的並發數
conn = pymysql.connect(host=‘‘, port=, user=‘‘, passwd=‘‘, db=‘‘)
cus = conn.curse()
2. 實行sql
sql = "select * from Student;"
cus.execute(sql)
cus.fetchone()  獲取單個  返回值  tuple
cus.fetchall()  獲取多個  返回值  list（單個元素是tuple）
cus.fetchmany(size=n)  獲取多個
3. 關閉遊標和連接
cus.close()
conn.close()
註意結合try exception finally的使用


SQLAlchemy
1. 創建引擎
engine = create_engine(‘mysql+pymysql://username:password@hostname:port/db‘)
2. 創建session
DBsession = sessionmaker(bind=engine)
session = DBsession()

3.創建表
a. 獲得engine
b. metadata = MetaData(engine)
c. student = Table(‘表名‘, metadata, Colume(‘id‘, Integer, primary_key=True), Colume(‘name‘, String(50))
d. metadata.create_all()

4.增加
a. 先要有一個模型
Base = declarative_base(0
class Student(Base):
    __tablename__ = ‘student‘
    id = Column(Integer, primary_key=True)
    name = Column(String(100), primary_key=True)

b. 導入模型類，實例化該類，
sutdent1 = Student(1, ‘ling‘)
c. session.add(單實例)      session.add_all([實例1, 實例2])

5. 查詢
filter和filter_by的區別
filter：可以使用>  < 等，但是列必須是： 表.列，   filter的等於號是==
session.query(Student).filter(Student.id>100)
filter 不支持組合查詢
session.query(Student).filter(Studnet.id>100).filter(name==‘ling‘)

filter_by： 可以直接寫列，不支持< >  filter_by 等於是==
session.query(Student).filter_by(id==10)
filter_by 可以支持組合查詢
session.query(Student).filter_by(name==‘ling‘ and id==‘342‘)

select * from student where name like ‘%ling%‘;
模糊查詢含有ling的關鍵字

模糊查詢
session.query(Student).filter(Student.name like(‘%ling%‘))

獲取數據的時候有兩個方法：
one()   tuple
all()   list(單個元素是tuple)
如果在查詢中不寫one(), 或者all()  出來的就是sql語句


6. 更新
1.  先查出來
2. 跟新一下類所對應的屬性值就ok
3. session.commit()
student1 = session.query(Student).filter(Student.id==1001)
student1.name = "test"
session.commit()

7. 刪除
1. 先查出來
2. 直接調用delete()方法就可以
3. 提交一下

8.統計， 分組，排序

統計：count()
只需要在查出來以後， 把one或者all替換成count()
統計有多少個

分組：group_by
查出來以後，把one或者all替換成group_by(屬性)

二、課堂案例如下

from sqlalchemy import create_engine, Integer, String, Column
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker

Base = declarative_base()
class Student(Base):
    __tablename__ = ‘student‘
    id = Column(Integer, primary_key=True)
    name = Column(String(100))
    age = Column(Integer)
    address = Column(String(100)）

def update(session):
    student1 = session.query(Student).filter(Student.id == 1001).one()
    student1.name=‘test123‘
    session.commit()
    student2 = session.query(Student).filter(Student.id == 1001).one()
    print(student2.name)
def delete(session):
    session.query(Student).filter(Student.id == 1001).delete()
    session.commit()

def insert(session):
    student1 = Student(id=1004, name=‘ling‘, age=28, address=‘shanxi‘)
    session.add(student1)
    session.commit()

def count(session):
    numnber = session.query(Student).filter().count()
    print("total student is {0}".format(numnber))

def groupBy(session):
    groupByAge = session.query(Student).group_by(Student.age).all()
    print(groupByAge)
    for i in groupByAge:
        print(i.id, i.name, i.age, i.address)

def orderBy(session):
    orderByAge = session.query(Student).order_by(Student.age.desc()).all()
    for x in orderByAge:
        print(x.id, x.name, x.age, x.address)

def main():
    engine = create_engine(‘mysql+pymysql://xiang:[email protected]/sqlalchemy‘)
    DBsession = sessionmaker(bind=engine)
    session = DBsession()
    # insert(session)
    # update(session)
    # delete(session)
    # count(session)
    # groupBy(session)
    orderBy(session)


if __name__ == ‘__main__‘:
    main()

復習&mysql