cx_Oracle使用方法二

下载地址：

https://pypi.python.org/pypi/cx_Oracle/5.2.1, 下载的时候注意数据库版本和操作系统环境。

技术手册：

http://cx-oracle.readthedocs.org/en/latest/index.html

cx_Oracle使用方法

正确安装好cx_oracle之后，要使用它来连接到oracle数据库进行操作，具体应该分3步走：

第一步：导入cx_Oracle ，建立连接

>>> import cx_Oracle      # 导入模块
>>> db = cx_Oracle.connect('hr', 'hrpwd', 'localhost:1521/XE') #建立连接，3 个参数分开写
>>> db1 = cx_Oracle.connect('hr/hrpwd@localhost:1521/XE') #建立连接，3 个参数连写
>>> dsn_tns = cx_Oracle.makedsn('localhost', 1521, 'XE')
>>> print dsn_tns
(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=localhost)(PORT=1521)))(CONNECT_DATA=(SID=XE)))
>>> db2 = cx_Oracle.connect('hr', 'hrpwd', dsn_tns)
>>> print db.version
10.2.0.1.0
>>> versioning = db.version.split('.')
>>> print versioning
['10', '2', '0', '1', '0']
>>> if versioning[0]=='10':
...      print "Running 10g"
... elif versioning[0]=='9':
...      print "Running 9i"
...
Running 10g
>>> print db.dsn
localhost:1521/XE

 

第二步：建立 Cursor 光标

 

>>>cursor = db.cursor() 
#建立一个cursor之后，我们可以调用这个cursor.execute（‘SQL‘） 来执行SQL语句。比如：
>>>cursor.execute(‘select * from tabs’)
#执行完毕以后，可以调用cursor.fetchall()一次取完所有结果，或者cursor.fetchone()一次取一行结果
>>> row=cursor.fetchall()
>>> for x in row:
        For y in x:
            Print y,
        Print

 

这样就可以按照表格的形式打印取得的结果了！

在从oracle取出数据的时候，考虑到它的数据类型了吗？下面就是数据类型的对应表

Datatypes

During the fetch stage, basic Oracle data types get mapped into their Python equivalents. cx_Oracle maintains a separate set of data types that helps in this transition. The Oracle - cx_Oracle - Python mappings are:

 

Oracle	cx_Oracle	Python
VARCHAR2 NVARCHAR2 LONG	cx_Oracle.STRING	str
CHAR	cx_Oracle.FIXED_CHAR
NUMBER	cx_Oracle.NUMBER	int
FLOAT		float
DATE	cx_Oracle.DATETIME	datetime.datetime
TIMESTAMP	cx_Oracle.TIMESTAMP
CLOB	cx_Oracle.CLOB	cx_Oracle.LOB
BLOB	cx_Oracle.BLOB

 

带参数的查询：

>>> named_params = {'dept_id':50, 'sal':1000}
>>> query1 = cursor.execute('SELECT * FROM employees WHERE department_id=:dept_id AND salary>:sal', named_params)
>>> query2 = cursor.execute('SELECT * FROM employees WHERE department_id=:dept_id AND salary>:sal', dept_id=50, sal=1000)

这种是名字参数，还可以按位置参数：

r1 = cursor.execute('SELECT * FROM locations WHERE country_id=:1 AND city=:2', ('US', 'Seattle'))

注意：

当只有一次参数的时候，也要把它写成元组的形式，比如

Cursor.execute(‘select name from user where id=:1’,(login_Id,))

千万要注意，login_id后面还带有一个逗号，如果没有逗号，他其实就是一个数据对象，但是当他后面有个逗号的时候，他就变成了元组的一个数据项，千万要记住啊，我就是在这里徘徊了很久。！

Cursor. Prepare的用法，

这个方法就是在prepare之后，你再去execute的时候，就不用写上sql语句参数了

>>> cursor.prepare('SELECT * FROM jobs WHERE min_salary>:min')
>>> r = cursor.execute(None, {'min':1000}) #注意，第一个参数是None

一次执行多条sql语句：
Large insert operations don't require many separate inserts because Python fully supports inserting many rows at once with the cx_Oracle.Cursor.executemany method. Limiting the number of execute operations improves program performance a lot and should be the first thing to think about when writing applications heavy on INSERTs.
Let's create a table for a Python module list, this time directly from Python. You will drop it later.

>>> create_table = """
CREATE TABLE python_modules (
module_name VARCHAR2(50) NOT NULL,
file_path VARCHAR2(300) NOT NULL
)
"""
>>> from sys import modules
>>> cursor.execute(create_table)
>>> M = []
>>> for m_name, m_info in modules.items():
...     try:
...       M.append((m_name, m_info.__file__))
...     except AttributeError:
...       pass
...
>>> len(M)
76
>>> cursor.prepare("INSERT INTO python_modules(module_name, file_path) VALUES (:1, :2)")
>>> cursor.executemany(None, M)
>>> db.commit()
>>> r = cursor.execute("SELECT COUNT(*) FROM python_modules")
>>> print cursor.fetchone()
(76,)
>>> cursor.execute("DROP TABLE python_modules PURGE")

 

BLOB & CLOB 格式的创建:

binary_content = cursor.var(cx_Oracle.BLOB)
binary_content.setvalue(0, content)