Python SQLite3简介

最近需要用Python写一个简易通讯录，但是对于数据存储很发愁。大家都知道，使用 Python 中的列表和字典进行存储数据是很不靠谱的，所以就想到Python有没有内置的数据库模块。

SQLite3简介

SQLite3 可使用 sqlite3 模块与 Python 进行集成。sqlite3 模块是由 Gerhard Haring 编写的。它提供了一个与 PEP 249 描述的 DB-API 2.0 规范兼容的 SQL 接口。您不需要单独安装该模块，因为 Python 2.5.x 以上版本默认自带了该模块。
为了使用 sqlite3 模块，您首先必须创建一个表示数据库的连接对象，然后您可以有选择地创建光标对象，这将帮助您执行所有的 SQL 语句。

怎么样，听起来不错吧！那就快来学习使用吧。

连接数据库

下面的 Python 代码显示了如何连接到一个现有的数据库。如果数据库不存在，那么它就会被创建，最后将返回一个数据库对象。

#-*- coding:utf-8 -*-
import sqlite3
conn = sqlite3.connect('mysql_person.db')

print "Opened database successfully";

在这里，您也可以把数据库名称复制为特定的名称 :memory:，这样就会在 RAM 中创建一个数据库。现在，让我们来运行上面的程序，在当前目录中创建我们的数据库 mysql_person.db。您可以根据需要改变路径。保存上面代码到 sqlite.py 文件中，并按如下所示执行。如果数据库成功创建，那么会显示下面所示的消息：

$chmod +x sqlite.py
$./sqlite.py
Open database successfully

创建表

下面的 Python 代码段将用于在先前创建的数据库中创建一个表：

#-*- coding:utf-8 -*-

import sqlite3

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

conn.execute('''CREATE TABLE MT
    (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()

上述程序执行时，它会在 test.db 中创建 MT 表，并显示下面所示的消息：

Opened database successfully
Table created successfully

INSERT 操作

下面的 Python 程序显示了如何在上面创建的 MT 表中创建记录：

#-*- coding:utf-8 -*-

import sqlite3

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

conn.execute("INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) \
   VALUES (1, 'Paul', 32, 'California', 20000.00 )");

conn.execute("INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) \
   VALUES (2, 'Allen', 25, 'Texas', 15000.00 )");

conn.execute("INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) \
   VALUES (3, 'Teddy', 23, 'Norway', 20000.00 )");

conn.execute("INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) \
   VALUES (4, 'Mark', 25, 'Rich-Mond ', 65000.00 )");

conn.commit()
print "Records created successfully";
conn.close()

上述程序执行时，它会在 MT 表中创建给定记录，并会显示以下两行：

Opened database successfully
Records created successfully

SELECT 操作

下面的 Python 程序显示了如何从前面创建的 MT 表中获取并显示记录：

#-*- coding:utf-8 -*-

import sqlite3

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

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

print "Operation done successfully";
conn.close()

上述程序执行时，它会产生以下结果：

Opened database successfully
ID = 1
NAME = Paul
ADDRESS = California
SALARY = 20000.0

ID = 2
NAME = Allen
ADDRESS = Texas
SALARY = 15000.0

ID = 3
NAME = Teddy
ADDRESS = Norway
SALARY = 20000.0

ID = 4
NAME = Mark
ADDRESS = Rich-Mond
SALARY = 65000.0

Operation done successfully

UPDATE 操作

下面的 Python 代码显示了如何使用 UPDATE 语句来更新任何记录，然后从 COMPANY 表中获取并显示更新的记录：

#-*- coding:utf-8 -*-

import sqlite3

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

conn.execute("UPDATE COMPANY set SALARY = 25000.00 where ID=1")
conn.commit()
print "Total number of rows updated :", conn.total_changes

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

print "Operation done successfully";
conn.close()

上述程序执行时，它会产生以下结果：

Opened database successfully
Total number of rows updated : 1
ID = 1
NAME = Paul
ADDRESS = California
SALARY = 25000.0

ID = 2
NAME = Allen
ADDRESS = Texas
SALARY = 15000.0

ID = 3
NAME = Teddy
ADDRESS = Norway
SALARY = 20000.0

ID = 4
NAME = Mark
ADDRESS = Rich-Mond
SALARY = 65000.0

Operation done successfully

DELETE 操作

下面的 Python 代码显示了如何使用 DELETE 语句删除任何记录，然后从 COMPANY 表中获取并显示剩余的记录：

#-*- coding:utf-8 -*-

import sqlite3

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

conn.execute("DELETE from COMPANY where ID=2;")
conn.commit()
print "Total number of rows deleted :", conn.total_changes

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

print "Operation done successfully";
conn.close()

上述程序执行时，它会产生以下结果：

Opened database successfully
Total number of rows deleted : 1
ID = 1
NAME = Paul
ADDRESS = California
SALARY = 20000.0

ID = 3
NAME = Teddy
ADDRESS = Norway
SALARY = 20000.0

ID = 4
NAME = Mark
ADDRESS = Rich-Mond
SALARY = 65000.0

Operation done successfully