day12 python学习随笔 中
SQLAlchemy是Python编程语言下的一款ORM框架，该框架建立在数据库API之上，使用关系对象映射进行数据库操作，简言之
便是：将对象转换成SQL，然后使用数据API执行SQL并获取执行结果。
Dialect用于和数据API进行交流，根据配置文件的不同调用不同的数据库API，从而实现对数据库的操作，如：
MySQL
-
Python
mysql
+
mysqldb:
/
/
<user>:<password>@<host>[:<port>]
/
<dbname>
pymysql
mysql
+
pymysql:
/
/
<username>:<password>@<host>
/
<dbname>[?<options>]
MySQL
-
Connector
mysql
+
mysqlconnector:
/
/
<user>:<password>@<host>[:<port>]
/
<dbname>
cx_Oracle
oracle
+
cx_oracle:
/
/
user:
pass
@host:port
/
dbname[?key
=
value&key
=
value...]
更多详见：http:
/
/
docs.sqlalchemy.org
/
en
/
latest
/
dialects
/
index.html
步骤一：
使用 Engine/ConnectionPooling/Dialect 进行数据库操作，Engine使用ConnectionPooling连接数据库，然后再通过Dialect执行SQL语句。
#!/usr/bin/env python
# -*- coding:utf-8 -*-
from
sqlalchemy
import
create_engine
engine.execute(
"INSERT INTO ts_test (a, b) VALUES ('2', 'v1')"
)
engine.execute(
"INSERT INTO ts_test (a, b) VALUES (%s, %s)"
,
((
555
,
"v1"
),(
666
,
"v1"
),)
)
engine.execute(
"INSERT INTO ts_test (a, b) VALUES (%(id)s, %(name)s)"
,
id
=
999
, name
=
"v1"
)
result
=
engine.execute(
'select * from ts_test'
)
result.fetchall()
#!/usr/bin/env python
# -*- coding:utf-8 -*-
from sqlalchemy import create_engine
engine = create_engine("mysql+mysqldb://root:[email protected]:3306/s11", max_overflow=5)
# 事务操作
with engine.begin() as conn:
conn.execute("insert into table (x, y, z) values (1, 2, 3)")
conn.execute("my_special_procedure(5)")
conn = engine.connect()
# 事务操作
with conn.begin():
conn.execute("some statement", {'x':5, 'y':10})
事务操作
注：查看数据库连接：show status like 'Threads%';
步骤二：
使用 Schema Type/SQL Expression Language/Engine/ConnectionPooling/Dialect 进行数据库操作。Engine使用Schema Type创建一个特定的结构对象，之后通过SQL Expression Language将该对象转换成SQL语句，然后通过 ConnectionPooling 连接数据库，再然后通过 Dialect 执行SQL，并获取结果。
#!/usr/bin/env python
# -*- coding:utf-8 -*-
from sqlalchemy import create_engine, Table, Column, Integer, String, MetaData, ForeignKey
metadata = MetaData()
user = Table('user', metadata,
Column('id', Integer, primary_key=True),
Column('name', String(20)),
)
color = Table('color', metadata,
Column('id', Integer, primary_key=True),
Column('name', String(20)),
)
engine = create_engine("mysql+mysqldb://root:[email protected]:3306/s11", max_overflow=5)
metadata.create_all(engine)
# metadata.clear()
# metadata.remove()
#!/usr/bin/env python
# -*- coding:utf-8 -*-
from sqlalchemy import create_engine, Table, Column, Integer, String, MetaData, ForeignKey
metadata = MetaData()
user = Table('user', metadata,
Column('id', Integer, primary_key=True),
Column('name', String(20)),
)
color = Table('color', metadata,
Column('id', Integer, primary_key=True),
Column('name', String(20)),
)
engine = create_engine("mysql+mysqldb://root:[email protected]:3306/s11", max_overflow=5)
conn = engine.connect()
# 创建SQL语句，INSERT INTO "user" (id, name) VALUES (:id, :name)
conn.execute(user.insert(),{'id':7,'name':'seven'})
conn.close()
# sql = user.insert().values(id=123, name='wu')
# conn.execute(sql)
# conn.close()
# sql = user.delete().where(user.c.id > 1)
# sql = user.update().values(fullname=user.c.name)
# sql = user.update().where(user.c.name == 'jack').values(name='ed')
# sql = select([user, ])
# sql = select([user.c.id, ])
# sql = select([user.c.name, color.c.name]).where(user.c.id==color.c.id)
# sql = select([user.c.name]).order_by(user.c.name)
# sql = select([user]).group_by(user.c.name)
# result = conn.execute(sql)
# print result.fetchall()
# conn.close()
增删改查
更多内容详见：
http://www.jianshu.com/p/e6bba189fcbd
http://docs.sqlalchemy.org/en/latest/core/expression_api.html
注：SQLAlchemy无法修改表结构，如果需要可以使用SQLAlchemy开发者开源的另外一个软件Alembic来完成。