一、复习详尽如下：

创建一个test库

create database test;

授权一个用户

grant all privileges on *.* to 'xiang'@'%' identified by '1qaz@WSX';

创建表

create table student(id int not null);

查询

select * from tabel_name where 条件1 and 条件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 条件判断

删除

delete from table_name where 条件判断

drop table table_name

联合查询

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

创建索引

create index idx_库名_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'

链接数据库

Python2 使用的是MySQLdb

python3 使用的pymysql pip安装

1. 创建链接和游标

注意：在mysql连接中，尽量使用一个连接，确保mysql的并发数

conn = pymysql.connect(host='', port=, user='', passwd='', db='')

cus = conn.curse()

2. 实行sql

sql = "select * from Student;"

cus.execute(sql)

cus.fetchone() 获取单个 返回值 tuple

cus.fetchall() 获取多个 返回值 list(单个元素是tuple)

cus.fetchmany(size=n) 获取多个

3. 关闭游标和连接

cus.close()

conn.close()

注意结合try exception finally的使用

SQLAlchemy

1. 创建引擎

engine = create_engine('mysql+pymysql://username:password@hostname:port/db')

2. 创建session

DBsession = sessionmaker(bind=engine)

session = DBsession()

3.创建表

a. 获得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. 先要有一个模型

Base = declarative_base(0

class Student(Base):

__tablename__ = 'student'

id = Column(Integer, primary_key=True)

name = Column(String(100), primary_key=True)

b. 导入模型类，实例化该类，

sutdent1 = Student(1, 'ling')

c. session.add(单实例) session.add_all([实例1, 实例2])

5. 查询

filter和filter_by的区别

filter：可以使用> < 等，但是列必须是： 表.列， filter的等于号是==

session.query(Student).filter(Student.id>100)

filter 不支持组合查询

session.query(Student).filter(Studnet.id>100).filter(name=='ling')

filter_by： 可以直接写列，不支持< > filter_by 等于是==

session.query(Student).filter_by(id==10)

filter_by 可以支持组合查询

session.query(Student).filter_by(name=='ling' and id=='342')

select * from student where name like '%ling%';

模糊查询含有ling的关键字

模糊查询

session.query(Student).filter(Student.name like('%ling%'))

获取数据的时候有两个方法：

one() tuple

all() list(单个元素是tuple)

如果在查询中不写one(), 或者all() 出来的就是sql语句

6. 更新

1. 先查出来

2. 跟新一下类所对应的属性值就ok

3. session.commit()

student1 = session.query(Student).filter(Student.id==1001)

student1.name = "test"

session.commit()

7. 删除

1. 先查出来

2. 直接调用delete()方法就可以

3. 提交一下

8.统计， 分组，排序

统计：count()

只需要在查出来以后， 把one或者all替换成count()

统计有多少个

分组：group_by

查出来以后，把one或者all替换成group_by(属性)

二、课堂案例如下

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:xiang@192.168.48.136/sqlalchemy')

DBsession = sessionmaker(bind=engine)

session = DBsession()

# insert(session)

# update(session)

# delete(session)

# count(session)

# groupBy(session)

orderBy(session)

if __name__ == '__main__':

main()