python postgresql跨数据库操作_Python 操作 PostgreSQL 数据库

最新推荐文章于 2021-06-09 11:13:44 发布

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最新推荐文章于 2021-06-09 11:13:44 发布

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文章标签： python postgresql跨数据库操作

本文介绍了如何使用Python的psycopg2模块与PostgreSQL数据库进行交互，包括连接数据库、创建表、插入数据、查询数据、更新记录以及删除记录等基本操作。示例代码详细展示了每一步骤的实现过程。

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我使用的是 Python 3.7.0

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。

pip3 install python-psycopg2

pip3 install psycopg2-binary

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 inrows:

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= 1NAME=Paul

ADDRESS=California

SALARY= 20000.0ID= 2NAME=Allen

ADDRESS=Texas

SALARY= 15000.0ID= 3NAME=Teddy

ADDRESS=Norway

SALARY= 20000.0ID= 4NAME=Mark

ADDRESS= Rich-Mond

SALARY= 65000.0Operation 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 inrows:

print("ID =", row[0])

print("NAME =", row[1])

print("ADDRESS =", row[2])

print("SALARY =", row[3], "\n")print("Operation done successfully");

conn.close()

Python

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 inrows:

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

https://www.yiibai.com/postgresql/postgresql_python.html