一、对MySQL的操作

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);
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、session用法

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()

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