SQLAlchemy是Python編程語言下的一款ORM框架,該框架建立在數據庫API之上,使用關係對象映射進行數據庫操作,簡言之便是:將對象轉換成SQL,然後使用數據API執行SQL並獲取執行結果。
Dialect用於和數據API進行交流,根據配置文件的不同調用不同的數據庫API,從而實現對數據庫的操作,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...]
更多詳見:http:
/
/
docs.sqlalchemy.org
/
en
/
latest
/
dialects
/
index.html
步驟一:
使用 Engine/ConnectionPooling/Dialect 進行數據庫操作,Engine使用ConnectionPooling連接數據庫,然後再通過Dialect執行SQL語句。
#!/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) # 事務操作 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() # 事務操作 with conn.begin(): conn.execute("some statement", {'x':5, 'y':10}) 事務操作
注:查看數據庫連接:show status like 'Threads%';
步驟二:
使用 Schema Type/SQL Expression Language/Engine/ConnectionPooling/Dialect 進行數據庫操作。Engine使用Schema Type創建一個特定的結構對象,之後通過SQL Expression Language將該對象轉換成SQL語句,然後通過 ConnectionPooling 連接數據庫,再然後通過 Dialect 執行SQL,並獲取結果。
#!/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() # 創建SQL語句,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() 增刪改查
更多內容詳見:
http://www.jianshu.com/p/e6bba189fcbd
http://docs.sqlalchemy.org/en/latest/core/expression_api.html
注:SQLAlchemy無法修改表結構,如果需要可以使用SQLAlchemy開發者開源的另外一個軟件Alembic來完成。