Python连接Oracle之环境配置、实例代码及报错解决方法详解

Oracle Client 安装

1、环境

日期：2019年8月1日

公司已经安装好Oracle服务端

Windows版本：Windows10专业版

系统类型：64位操作系统，基于x64的处理器

Python版本：Python 3.6.4 :: Anaconda, Inc.

2、下载网址

https://www.oracle.com/database/technologies/instant-client/downloads.html

3、解压至目录

解压后（这里放D盘）

4、配置环境变量

控制面板\系统和安全\系统 -> 高级系统设置 -> 环境变量

新建ORACLE_HOME，值为包解压的路径

编辑PATH，添加%ORACLE_HOME%

Navicat连接测试

cx_Oracle

安装命令

conda install cx_Oracle

基础代码

import cx_Oracle
def execute(query):
  db = cx_Oracle.connect('用户名/密码@IP/ServiceName')
  cursor = db.cursor()
  cursor.execute(query)
  result = cursor.fetchall()
  cursor.close()
  db.close()
  return result
def commit(sql):
  db = cx_Oracle.connect('用户名/密码@IP/ServiceName')
  cursor = db.cursor()
  cursor.execute(sql)
  db.commit()
  cursor.close()
  db.close()

封装成类

from cx_Oracle import Connection # conda install cx_Oracle
from conf import CONN, Color
class Oracle(Color):
  def __init__(self, conn=CONN):
    self.db = Connection(*conn, encoding='utf8') # 用户名 密码 IP/ServiceName
    self.cursor = self.db.cursor()
  def __del__(self):
    self.cursor.close()
    self.db.close()
  def commit(self, sql):
    try:
      self.cursor.execute(sql)
      self.db.commit()
    except Exception as e:
      self.red(e)
  def fetchall(self, query):
    self.cursor.execute(query)
    return self.cursor.fetchall()
  def fetchone(self, query, n=9999999):
    self.cursor.execute(query)
    for _ in range(n):
      one = self.cursor.fetchone()
      if one:
        yield one
  def fetchone_dt(self, query, n=9999999):
    self.cursor.execute(query)
    columns = [i[0] for i in self.cursor.description]
    length = len(columns)
    for _ in range(n):
      one = self.cursor.fetchone() # tuple
      yield {columns[i]: one[i] for i in range(length)}
  def read_clob(self, query):
    self.cursor.execute(query)
    one = self.cursor.fetchone()
    while one:
      try:
        yield one[0].read()
      except Exception as e:
        self.red(e)
      one = self.cursor.fetchone()
  def db2sheet(self, query, prefix):
    df = pd.read_sql_query(query, self.db)
    if 'url' in df.columns:
      df['url'] = "'" + df['url']
    df.to_excel(prefix.replace('.xlsx', '')+'.xlsx', index=False)
  def db2sheets(self, queries, prefix):
    writer = pd.ExcelWriter(prefix.replace('.xlsx', '')+'.xlsx')
    for sheet_name, query in queries.items():
      df = pd.read_sql_query(query, self.db)
      if 'url' in df.columns:
        df['url'] = "'" + df['url']
      df.to_excel(writer, sheet_name=sheet_name, index=False)
    writer.save()
  def tb2sheet(self, table):
    sql = "SELECT * FROM " + table
    self.db2sheet(sql, table)
  def insert(self, dt, tb):
    for k, v in dt.items():
      if isinstance(v, str):
        dt[k] = v.replace("'", '').strip()
    ls = [(k, v) for k, v in dt.items() if v is not None]
    sql = 'INSERT INTO %s (' % tb + ','.join(i[0] for i in ls) + \
       ') VALUES (' + ','.join('%r' % i[1] for i in ls) + ')'
    self.commit(sql)
  def insert_clob(self, dt, tb, clob):
    for k, v in dt.items():
      if isinstance(v, str):
        dt[k] = v.replace("'", '').strip()
    # 把超长文本保存在一个变量中
    # declare = "DECLARE variate CLOB := '%s';\n" % dt[clob]
    join = lambda x: '||'.join("'%s'" % x[10922*i: 10922*(i+1)] for i in range(len(x)//10922+1)) # 32768//3
    declare = "DECLARE variate CLOB := %s;\n" % join(dt[clob])
    dt[clob] = 'variate'
    ls = [(k, v) for k, v in dt.items() if v is not None]
    sql = 'INSERT INTO %s (' % tb + ','.join(i[0] for i in ls) + ') VALUES (' +\
       ','.join('%r' % i[1] for i in ls) + ');'
    sql = declare + 'BEGIN\n%s\nEND;' % sql.replace("'variate'", 'variate')
    self.commit(sql)
  def update(self, dt_update, dt_condition, table):
    sql = 'UPDATE %s SET ' % table + ','.join('%s=%r' % (k, v) for k, v in dt_update.items()) \
       + ' WHERE ' + ' AND '.join('%s=%r' % (k, v) for k, v in dt_condition.items())
    self.commit(sql)
  def truncate(self, tb):
    self.commit('truncate table ' + tb)
db_read = Oracle()
fetchall = db_read.fetchall
fetchone = db_read.fetchone
read_clob = db_read.read_clob
if __name__ == '__main__':
  query = '''
  '''.strip()
  for i in fetchone(query, 99):
    print(i)

conf

CONN = ('用户名', '密码', 'IP/ServiceName')
conn = '用户名/密码@IP/ServiceName'

文本字符串查询

class INSTR(Oracle):
  """文本字符串查询"""
  def highlight_instr(self, table, field, keyword, clob=True):
    sql = "SELECT %s FROM %s WHERE INSTR(%s,'%s')>0" % (field, table, field, keyword)
    if clob:
      for i in self.read_clob(sql):
        self.highlight(i, keyword)
    else:
      for i, in self.fetchone(sql):
        self.highlight(i, keyword)
  def regexp_instr(self, table, field, pattern, regexp=True, clob=True):
    sql = "SELECT %s FROM %s WHERE INSTR(%s,'%s')>0" % (field, table, field, pattern)
    sql = sql.replace('INSTR', 'REGEXP_INSTR') if regexp else sql
    if clob:
      for i in self.read_clob(sql):
        yield i
    else:
      for i, in self.fetchone(sql):
        yield i

一个简单的建表示例

-- 建表
CREATE TABLE table_name
(
serial_number   NUMBER(10),
collect_date   DATE,
url        VARCHAR2(255),
long_text     CLOB,
price       NUMBER(10)-- 若需要精确到小数点2位，按分存储，/100还原到元
);
-- 给表添加备注
COMMENT ON TABLE table_name IS '中文表名';
-- 给表字段添加备注
COMMENT ON COLUMN table_name.serial_number IS '编号';
COMMENT ON COLUMN table_name.collect_date IS '日期';
COMMENT ON COLUMN table_name.url IS 'URL';
COMMENT ON COLUMN table_name.long_text IS '长文本';
COMMENT ON COLUMN table_name.price IS '价钱';
-- 插入
INSERT INTO table_name(collect_date) VALUES (DATE'2019-08-23');
INSERT INTO table_name(long_text) VALUES ('a');
INSERT INTO table_name(long_text) VALUES ('b');
-- 查询
SELECT * FROM table_name WHERE TO_CHAR(long_text) in ('a','b');
-- 查建表语句（表名大写）
SELECT dbms_metadata.get_ddl('TABLE','TABLE_NAME') FROM dual;
-- 删表
DROP TABLE table_name;

sqlalchemy

import os # 解决【UnicodeEncodeError: 'ascii' codec can't encode character】问题
os.environ['NLS_LANG'] = 'AMERICAN_AMERICA.AL32UTF8'
# os.environ['NLS_LANG'] = 'SIMPLIFIED CHINESE_CHINA.UTF8'
from cx_Oracle import makedsn
from sqlalchemy import create_engine, Column, String, Integer
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker
# 连接数据库（ORA-12505: TNS:listener does not currently know of SID given in connect descriptor）
ip = ''
port = ''
tnsname = '' # 实例名
uname = '' # 用户名
pwd = '' # 密码
dsnStr = makedsn(ip, port, service_name=tnsname)
connect_str = "oracle://%s:%s@%s" % (uname, pwd, dsnStr)
# 创建连接引擎，这个engine是lazy模式，直到第一次被使用才真实创建
engine = create_engine(connect_str, encoding='utf-8')
# 创建对象的基类
Base = declarative_base()
class Student(Base):
  # 表名
  __tablename__ = 'student'
  # 表字段
  sid = Column(String(20), primary_key=True)
  age = Column(Integer)
# 建表（继承Base的所有表）
Base.metadata.create_all(bind=engine)
# 使用ORM操作数据库
Session = sessionmaker(bind=engine) # 创建ORM基类
session = Session() # 创建ORM对象
tb_obj = Student(sid='a6', age=18) # 创建表对象
session.add(tb_obj) # 添加到ORM对象（插入数据）
session.commit() # 提交
session.close() # 关闭ORM对象
# 删表（继承Base的所有表）
Base.metadata.drop_all(engine)

报错处理

DPI-1047: 64-bit Oracle Client library cannot be loaded

首先操作系统位数、python位数、cx_Oracle版本要对应上；另外可能缺【Visual C++】

每次装完后，要重启pycharm和python

ORA-12170: TNS:Connect timeout occurred

打开终端ping一下

检查【主机名或IP地址】、【服务名或SID】、【用户名】和【密码】是否填对

中文乱码

encoding=‘utf8'

ORA-00972: identifier is too long

insert语句中出现'之类的字符

解决方法：将可能报错的字符替换掉

ORA-64203: Destination buffer too small to hold CLOB data after character set conversion.

select TO_CHAR(long_text) from table_name，目标缓冲区太小，无法储存CLOB转换字符后的数据

解决方法：不在SQL用TO_CHAR，改在Python中用read（如上代码所示）

ORA-01704: string literal too long

虽然CLOB可以保存长文本，但是SQL语句有长度限制

解决方法：把超长文本保存在一个变量中（如上代码所示）

PLS-00172: string literal too long

字符串长度>32767(215-1)

解决方法：使用'||'来连接字符串（如上代码所示）

ORA-00928: missing SELECT keyword

INSERT操作时，表字段命名与数据库内置名称冲突，如：ID、LEVEL、DATE等

解决方法：建立命名规范

cx_Oracle.DatabaseError: ORA-12505: TNS:listener does not currently know of SID given in connect descriptor

使用sqlalchemy时的报错

原因可能是目标数据库是集群部署的，可以咨询一下DBA，或见上面代码from cx_Oracle import makedsn

UnicodeEncodeError: 'ascii' codec can't encode character

使用sqlalchemy时的报错，插入中文字符引起

解决方法是设置os.environ['NLS_LANG']

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