postgresql数据库-Python连接PostgreSQL数据库

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PostgreSQL可以使用psycopg2模块与Python集成。sycopg2是用于Python编程语言的PostgreSQL数据库适配器。 psycopg2是非常小,快速,稳定的。 您不需要单独安装此模块,因为默认情况下它会随着Python 2.5.x版本一起发布。 如果还没有在您的机器上安装它,那么可以使用yum命令安装它,如下所示:

$yum install python-psycopg2 

要使用psycopg2模块,必须首先创建一个表示数据库的Connection对象,然后可以选择创建可以帮助您执行所有SQL语句的游标对象。

连接到数据库

以下Python代码显示了如何连接到现有的数据库。 如果数据库不存在,那么它将自动创建,最后将返回一个数据库对象。

#!/usr/bin/python  import psycopg2  conn = psycopg2.connect(database="testdb", user="postgres", password="pass123", host="127.0.0.1", port="5432")  print "Opened database successfully" 

在这里指定使用testdb作为数据库名称,如果数据库已成功打开连接,则会提供以下消息:

Open database successfully 

创建表

以下Python程序将用于在先前创建的数据库(testdb)中创建一个表:

#!/usr/bin/python  import psycopg2  conn = psycopg2.connect(database="testdb", user="postgres", password="pass123", host="127.0.0.1", port="5432") print "Opened database successfully"  cur = conn.cursor() cur.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() conn.close() 

当执行上述程序时,它将在数据库testdb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程序显示了如何在上述示例中创建的COMPANY表中创建记录:

#!/usr/bin/python  import psycopg2  conn = psycopg2.connect(database="testdb", user="postgres", password="pass123", host="127.0.0.1", port="5432") print "Opened database successfully"  cur = conn.cursor()  cur.execute("INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) /       VALUES (1, 'Paul', 32, 'California', 20000.00 )");  cur.execute("INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) /       VALUES (2, 'Allen', 25, 'Texas', 15000.00 )");  cur.execute("INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) /       VALUES (3, 'Teddy', 23, 'Norway', 20000.00 )");  cur.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() 

当执行上述程序时,它将在COMPANY表中创建/插入给定的记录,并显示以下两行:

Opened database successfully Records created successfully 

SELECT操作

以下Python程序显示了如何从上述示例中创建的COMPANY表中获取和显示记录:

#!/usr/bin/python  import psycopg2  conn = psycopg2.connect(database="testdb", user="postgres", password="pass123", host="127.0.0.1", port="5432") print "Opened database successfully"  cur = conn.cursor()  cur.execute("SELECT id, name, address, salary  from COMPANY") rows = cur.fetchall() for row in rows:    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,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 

更新操作

以下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:

#!/usr/bin/python  import psycopg2  conn = psycopg2.connect(database="testdb", user="postgres", password="pass123", host="127.0.0.1", port="5432") print "Opened database successfully"  cur = conn.cursor()  cur.execute("UPDATE COMPANY set SALARY = 25000.00 where ID=1") conn.commit print "Total number of rows updated :", cur.rowcount  cur.execute("SELECT id, name, address, salary  from COMPANY") rows = cur.fetchall() for row in rows:    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,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 

删除操作

以下Python代码显示了如何使用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 psycopg2  conn = psycopg2.connect(database="testdb", user="postgres", password="pass123", host="127.0.0.1", port="5432") print "Opened database successfully"  cur = conn.cursor()  cur.execute("DELETE from COMPANY where ID=2;") conn.commit print "Total number of rows deleted :", cur.rowcount  cur.execute("SELECT id, name, address, salary  from COMPANY") rows = cur.fetchall() for row in rows:    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,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 

  

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