python 操作PostgreSQL

2 connection.cursor()

该程序创建一个光标将用于整个数据库使用Python编程。 yiibai.com

3 cursor.execute(sql [, optional parameters])

此例程执行SQL语句。可被参数化的SQL语句（即占位符，而不是SQL文字）。 psycopg2的模块支持占位符用％s标志 yiibai.com

例如：cursor.execute("insert into people values (%s, %s)", (who, age))

 

4 curosr.executemany(sql, seq_of_parameters)

该程序执行SQL命令对所有参数序列或序列中的sql映射。 www.yiibai.com

5 curosr.callproc(procname[, parameters])

这个程序执行的存储数据库程序给定的名称。该程序预计为每一个参数，参数的顺序必须包含一个条目。

 

6 cursor.rowcount

这个只读属性，它返回数据库中的行的总数已修改，插入或删除最后 execute*().

 

7 connection.commit()

此方法提交当前事务。如果不调用这个方法，无论做了什么修改，自从上次调用commit()是不可见的，从其他的数据库连接。

 

8 connection.rollback()

此方法会回滚任何更改数据库自上次调用commit（）方法。

 

9 connection.close()

此方法关闭数据库连接。请注意，这并不自动调用commit（）。如果你只是关闭数据库连接而不调用commit（）方法首先，那么所有更改将会丢失！ www.yiibai.com

10 cursor.fetchone()

这种方法提取的查询结果集的下一行，返回一个序列，或者无当没有更多的数据是可用的。

 

11 cursor.fetchmany([size=cursor.arraysize])

这个例程中取出下一个组的查询结果的行数，返回一个列表。当没有找到记录，返回空列表。该方法试图获取尽可能多的行所显示的大小参数。

 

12 cursor.fetchall()

这个例程获取所有查询结果（剩余）行，返回一个列表。空行时则返回空列表。 www.yiibai.com

 

连接到数据库

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，最终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" 

创建表

以下Python程序将使用以前创建的数据库中创建一个表：

#!/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()

INSERT 操作

Python程序显示了我们如何创建表COMPANY 在上面的例子中创建表中的记录：

#!/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("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()

SELECT 操作

Python程序，显示如何获取并显示COMPANY 表在上面的例子中创建的记录：

#!/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("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()  

当上述程序执行时，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

Python代码显示如何，我们可以使用UPDATE语句来更新记录，然后从COMPANY表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()  

DELETE 操作

Python代码显示了如何我们可以使用DELETE语句删除记录，然后获取并显示COMPANY 表剩余的记录： 

#!/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() 

 

python 操作PostgreSQL

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