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")

自： http://www.x5dj.com/Blog/00182202/00572497.shtml