Python连接SQLite数据库

由Gerhard Haring编写的sqlite3模块与Python进行集成。 它提供了符合由PEP 249描述的DB-API 2.0规范的SQL接口。所以不需要单独安装此模块,因为默认情况下随着Python 2.5.x以上版本一起发布运行。

要使用sqlite3模块,必须首先创建一个表示数据库的连接对象,然后可以选择创建的游标对象来执行SQL语句。

连接到数据库

以下Python代码显示了如何连接到一个指定的数据库。 如果数据库不存在,那么它将被创建,最后将返回一个数据库对象。

注意:在本示例中,使用的是 python 3.5.1

#!/usr/bin/python

import sqlite3

conn = sqlite3.connect('pydb.db')
print ("Opened database successfully");

在这里,还可以提供数据库名称作为特殊名称:memory:, 在RAM中创建数据库。 现在,运行上面的程序在当前目录中创建数据库:pydb.db

可以根据需要更改路径。 在F:\worksp\sqlite\py-sqlite.py文件中保留以上代码,并按如下所示执行。 如果数据库成功创建,则会提供以下消息:

《Python连接SQLite数据库》

创建表

以下Python程序将用于在先前创建的数据库(py-sqlite.py)中创建一个表:

#!/usr/bin/python

import sqlite3

## 打开数据库连接
conn = sqlite3.connect('py-sqlite.db')
print ("Opened database successfully");

## 创建一个表 - company
conn.execute('''CREATE TABLE company
       (ID INT PRIMARY KEY     NOT NULL,
       NAME           TEXT    NOT NULL,
       AGE            INT     NOT NULL,
       ADDRESS        CHAR(50),
       SALARY         REAL);''')
print ("Table created successfully");

conn.close()

当执行上述程序后,将在py-sqlite.db中创建company表,并显示以下消息:

#!/usr/bin/python

import sqlite3

## 打开数据库连接
conn = sqlite3.connect('py-sqlite.db')
print ("Opened database successfully");

## 创建一个表 - company
conn.execute('''CREATE TABLE company
       (ID INT PRIMARY KEY     NOT NULL,
       NAME           TEXT    NOT NULL,
       AGE            INT     NOT NULL,
       ADDRESS        CHAR(50),
       SALARY         REAL);''')
print ("Table created successfully");

conn.close()

当执行上述程序时,它将在py-sqlite.db数据库中创建company表,并显示以下消息:

Opened database successfully
Table created successfully

插入操作

以下Python程序显示如何在上述示例中创建的COMPANY表中插入数据记录:

#!/usr/bin/python

import sqlite3

## 打开数据库连接
conn = sqlite3.connect('py-sqlite.db')
print ("Opened database successfully");

## 清除已存在的表 - company
conn.execute('''DROP TABLE company''');
conn.commit()

## 创建一个表 - company
conn.execute('''CREATE TABLE company
       (ID INT PRIMARY KEY     NOT NULL,
       NAME           TEXT    NOT NULL,
       AGE            INT     NOT NULL,
       ADDRESS        CHAR(50),
       SALARY         REAL);''')
print ("Table created successfully");

conn.commit()

## 插入数据
conn.execute("INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) \
      VALUES (1, 'Maxsu', 27, 'Haikou', 20000.00 )");

conn.execute("INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) \
      VALUES (2, 'Allen', 26, 'Shenzhen', 35000.00 )");

conn.execute("INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) \
      VALUES (3, 'Weiwang', 23, 'Guangzhou', 22000.00 )");

conn.execute("INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) \
      VALUES (4, 'Marklee', 25, 'Beijing', 45000.00 )");

conn.commit()
print ("Records Insert successfully");

conn.close()

当执行上述程序时,它将在COMPANY表中插入给定的数据记录,并显示以下结果:

Opened database successfully
Table created successfully
Records Insert successfully

SELECT/查询操作

以下Python程序显示如何从上述示例中创建的COMPANY表中获取并显示数据记录:

#!/usr/bin/python

import sqlite3

## 打开数据库连接
conn = sqlite3.connect('py-sqlite.db')
print ("Opened database successfully");

## 清除已存在的表 - company
conn.execute('''DROP TABLE company''');
conn.commit()

## 创建一个表 - company
conn.execute('''CREATE TABLE company
       (ID INT PRIMARY KEY     NOT NULL,
       NAME           TEXT    NOT NULL,
       AGE            INT     NOT NULL,
       ADDRESS        CHAR(50),
       SALARY         REAL);''')
print ("Table created successfully");

conn.commit()

## 插入数据
conn.execute("INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) \
      VALUES (1, 'Maxsu', 27, 'Haikou', 20000.00 )");

conn.execute("INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) \
      VALUES (2, 'Allen', 26, 'Shenzhen', 35000.00 )");

conn.execute("INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) \
      VALUES (3, 'Weiwang', 23, 'Guangzhou', 22000.00 )");

conn.execute("INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) \
      VALUES (4, 'Marklee', 25, 'Beijing', 45000.00 )");

conn.commit()
print ("Records Insert successfully");
print ('--------------------------- start fetch data from company --------------------------');

cursor = conn.execute("SELECT id, name, address, salary  from COMPANY")
for row in cursor:
   print ("ID = ", row[0])
   print ("NAME = ", row[1])
   print ("ADDRESS = ", row[2])
   print ("SALARY = ", row[3], "\n")

print ("Select Operation done successfully.");

conn.close()

执行上述程序时,会产生以下结果:

Opened database successfully
Table created successfully
Records Insert successfully
--------------------------- start fetch data from company --------------------------
ID =  1
NAME =  Maxsu
ADDRESS =  Haikou
SALARY =  20000.0 

ID =  2
NAME =  Allen
ADDRESS =  Shenzhen
SALARY =  35000.0 

ID =  3
NAME =  Weiwang
ADDRESS =  Guangzhou
SALARY =  22000.0 

ID =  4
NAME =  Marklee
ADDRESS =  Beijing
SALARY =  45000.0 

Select Operation done successfully.

更新操作

以下Python代码演示如何使用UPDATE语句来更新指定记录,然后再从COMPANY表中获取并显示更新的记录:

#!/usr/bin/python

import sqlite3

## 打开数据库连接
conn = sqlite3.connect('py-sqlite.db')
print ("Opened database successfully");

## 清除已存在的表 - company
conn.execute('''DROP TABLE company''');
conn.commit()

## 创建一个表 - company
conn.execute('''CREATE TABLE company
       (ID INT PRIMARY KEY     NOT NULL,
       NAME           TEXT    NOT NULL,
       AGE            INT     NOT NULL,
       ADDRESS        CHAR(50),
       SALARY         REAL);''')
print ("Table created successfully");

conn.commit()

## 插入数据
conn.execute("INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) \
      VALUES (1, 'Maxsu', 27, 'Haikou', 20000.00 )");

conn.execute("INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) \
      VALUES (2, 'Allen', 26, 'Shenzhen', 35000.00 )");

conn.execute("INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) \
      VALUES (3, 'Weiwang', 23, 'Guangzhou', 22000.00 )");

conn.execute("INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) \
      VALUES (4, 'Marklee', 25, 'Beijing', 45000.00 )");

conn.commit()

## 更新数据
conn.execute("UPDATE COMPANY set SALARY = 29999.00 where ID=1")
conn.commit()
print ("Total number of rows updated :", conn.total_changes)


print ("Records Insert successfully");
print ('--------------------------- start fetch data from company --------------------------');

cursor = conn.execute("SELECT id, name, address, salary  from COMPANY")
for row in cursor:
   print ("ID = ", row[0])
   print ("NAME = ", row[1])
   print ("ADDRESS = ", row[2])
   print ("SALARY = ", row[3], "\n")

print ("Select Operation done successfully.");

conn.close()

执行上述程序时,会产生以下结果:

Opened database successfully
Table created successfully
Total number of rows updated : 5
Records Insert successfully
--------------------------- start fetch data from company --------------------------
ID =  1
NAME =  Maxsu
ADDRESS =  Haikou
SALARY =  29999.0 

ID =  2
NAME =  Allen
ADDRESS =  Shenzhen
SALARY =  35000.0 

ID =  3
NAME =  Weiwang
ADDRESS =  Guangzhou
SALARY =  22000.0 

ID =  4
NAME =  Marklee
ADDRESS =  Beijing
SALARY =  45000.0 

Select Operation done successfully.

删除操作

以下Python代码演示如何使用DELETE语句来删除记录,然后从COMPANY表中获取并显示剩余的记录:

#!/usr/bin/python

import sqlite3

## 打开数据库连接
conn = sqlite3.connect('py-sqlite.db')
print ("Opened database successfully");

## 清除已存在的表 - company
conn.execute('''DROP TABLE company''');
conn.commit()

## 创建一个表 - company
conn.execute('''CREATE TABLE company
       (ID INT PRIMARY KEY     NOT NULL,
       NAME           TEXT    NOT NULL,
       AGE            INT     NOT NULL,
       ADDRESS        CHAR(50),
       SALARY         REAL);''')
print ("Table created successfully");

conn.commit()

## 插入数据
conn.execute("INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) \
      VALUES (1, 'Maxsu', 27, 'Haikou', 20000.00 )");

conn.execute("INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) \
      VALUES (2, 'Allen', 26, 'Shenzhen', 35000.00 )");

conn.execute("INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) \
      VALUES (3, 'Weiwang', 23, 'Guangzhou', 22000.00 )");

conn.execute("INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) \
      VALUES (4, 'Marklee', 25, 'Beijing', 45000.00 )");

conn.commit()

## 删除ID值小于等于2的数据
conn.execute("DELETE from COMPANY where ID<=2;")
conn.commit()

print ("Total number of rows updated :", conn.total_changes)


print ("Records Insert successfully");
print ('--------------------------- start fetch data from company --------------------------');

cursor = conn.execute("SELECT id, name, address, salary  from COMPANY")
for row in cursor:
   print ("ID = ", row[0])
   print ("NAME = ", row[1])
   print ("ADDRESS = ", row[2])
   print ("SALARY = ", row[3], "\n")

print ("Select Operation done successfully.");

conn.close()

执行上面语句后,得到以下结果 –

Opened database successfully
Table created successfully
Total number of rows updated : 6
Records Insert successfully
--------------------------- start fetch data from company --------------------------
ID =  3
NAME =  Weiwang
ADDRESS =  Guangzhou
SALARY =  22000.0 

ID =  4
NAME =  Marklee
ADDRESS =  Beijing
SALARY =  45000.0 

Select Operation done successfully.

这里只是简单演示如何使用Python来连接SQLite实现CURD操作,关于其它更复杂的操作,建议参考官方API和实例,这里就不是一一讲解了,如有问题欢迎留言。

        原文作者:SQLite教程
        原文地址: https://www.yiibai.com/sqlite/python-with-sqlite.html
        本文转自网络文章,转载此文章仅为分享知识,如有侵权,请联系博主进行删除。
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