简述
在本章中，您将学习如何在 Python 程序中使用 SQLite。安装
SQLite3 可以使用由 Gerhard Haring 编写的 sqlite3 模块与 Python 集成。它提供了一个符合 PEP 249 描述的 DB-API 2.0 规范的 SQL 接口。你不需要单独安装这个模块，因为它默认随 Python 2.5.x 版一起提供。 要使用 sqlite3 模块，您必须首先创建一个表示数据库的连接对象，然后您可以选择创建一个游标对象，这将帮助您执行所有 SQL 语句。Python sqlite3 模块 API
以下是重要的 sqlite3 模块例程，它们可以满足您从 Python 程序使用 SQLite 数据库的要求。如果您正在寻找更复杂的应用程序，那么您可以查看 Python sqlite3 模块的官方文档。连接到数据库
以下 Python 代码显示了如何连接到现有数据库。如果数据库不存在，则将创建它并最终返回一个数据库对象。#!/usr/bin/pythonimport sqlite3conn = sqlite3.connect('test.db')print "Opened database successfully"; 在这里，您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，让我们运行上面的程序来创建我们的数据库test.db在当前目录中。您可以根据需要更改路径。将上面的代码保存在 sqlite.py 文件中，然后按如下所示执行。如果数据库创建成功，则会显示以下消息。 $chmod +x sqlite.py$./sqlite.pyOpen database successfully 创建表
下面的 Python 程序将用于在之前创建的数据库中创建一个表。 #!/usr/bin/pythonimport sqlite3conn = sqlite3.connect('test.db')print "Opened database successfully";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() 当上面的程序被执行时，它会在你的目录中创建 COMPANY 表 test.db 它将显示以下消息 - Opened database successfullyTable created successfully 插入操作
下面的 Python 程序显示了如何在上面示例中创建的 COMPANY 表中创建记录。 #!/usr/bin/pythonimport sqlite3conn = sqlite3.connect('test.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() 执行上述程序时，它将在 COMPANY 表中创建给定的记录，并显示以下两行 - Opened database successfullyRecords created successfully 选择操作
以下 Python 程序显示了如何从上面示例中创建的 COMPANY 表中获取和显示记录。 #!/usr/bin/pythonimport sqlite3conn = sqlite3.connect('test.db')print "Opened database successfully";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 "Operation done successfully";conn.close() 执行上述程序时，将产生以下结果。 Opened database successfullyID = 1NAME = PaulADDRESS = CaliforniaSALARY = 20000.0ID = 2NAME = AllenADDRESS = TexasSALARY = 15000.0ID = 3NAME = TeddyADDRESS = NorwaySALARY = 20000.0ID = 4NAME = MarkADDRESS = Rich-MondSALARY = 65000.0Operation done successfully 更新操作
以下 Python 代码显示了如何使用 UPDATE 语句更新任何记录，然后从 COMPANY 表中获取并显示更新的记录。 #!/usr/bin/pythonimport sqlite3conn = sqlite3.connect('test.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_changescursor = 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 "Operation done successfully";conn.close() 执行上述程序时，将产生以下结果。 Opened database successfullyTotal number of rows updated : 1ID = 1NAME = PaulADDRESS = CaliforniaSALARY = 25000.0ID = 2NAME = AllenADDRESS = TexasSALARY = 15000.0ID = 3NAME = TeddyADDRESS = NorwaySALARY = 20000.0ID = 4NAME = MarkADDRESS = Rich-MondSALARY = 65000.0Operation done successfully 删除操作
以下 Python 代码展示了如何使用 DELETE 语句删除任何记录，然后从 COMPANY 表中获取并显示剩余记录。 #!/usr/bin/pythonimport sqlite3conn = sqlite3.connect('test.db')print "Opened database successfully";conn.execute("DELETE from COMPANY where ID = 2;")conn.commit()print "Total number of rows deleted :", conn.total_changescursor = 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 "Operation done successfully";conn.close() 执行上述程序时，将产生以下结果。 Opened database successfullyTotal number of rows deleted : 1ID = 1NAME = PaulADDRESS = CaliforniaSALARY = 20000.0ID = 3NAME = TeddyADDRESS = NorwaySALARY = 20000.0ID = 4NAME = MarkADDRESS = Rich-MondSALARY = 65000.0Operation done successfully
