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    postgresql怎么连接python

    爱喝马黛茶的安东尼爱喝马黛茶的安东尼2019-12-17 17:22:02原创2205

    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：

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    $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。

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    #!/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：

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    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：

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    #!/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：

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    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：

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    #!/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：

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    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：

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    #!/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：

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    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：

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    #!/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：

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    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：

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    #!/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：

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    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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