MySQLdb操作数据库（三）

删除数据
删除单条数据

#conding=utf-8
import MySQLdb
import random
try:
    conn = MySQLdb.connect(
        host = '127.0.0.1',
        user = 'root',
        passwd = "123456",
        port = 3306)

    conn.select_db('python')# 选择pythonDB数据库

    cur = conn.cursor()# 获取游标

    cur.execute("delete from user where id=0")
    cur.execute("select * from user")

    for v in cur.fetchall():
        print v

    cur.close()
    conn.commit()
    conn.close()
    print u"sql执行成功"
except Exception, e:
print e

删除多条数据

#conding=utf-8
import MySQLdb
import random
try:
    conn = MySQLdb.connect(
        host = '127.0.0.1',
        user = 'root',
        passwd = "123456",
        port = 3306)

    conn.select_db('python')# 选择pythonDB数据库

    cur = conn.cursor()# 获取游标

    sql = "delete from user where id=%s"
    cur.executemany(sql,[(3),(2,)])
    cur.execute("select * from user")

    for v in cur.fetchall():
        print v

    cur.close()
    conn.commit()
    conn.close()
    print u"sql执行成功"
except Exception, e:
    print e

事务回滚

import MySQLdb
import random
try:
    conn = MySQLdb.connect(
        host = '127.0.0.1',
        user = 'root',
        passwd = "123456",
        port = 3306)

    conn.select_db('python')# 
    cur = conn.cursor()# 获取游标
    cur.execute("select * from user")
    datas = cur.fetchall()
    print u"修改前的数据：\n", datas[0]

    cur.execute("update user set birthday='2100-08-12'where name='tom6")
    cur.execute("select * from user")
    datas = cur.fetchall()
    print u"修改后的数据：\n", datas[0]
    #回滚事务
    conn.rollback()
    cur.execute("select * from user")
    datas = cur.fetchall()
    print u"事务回滚后的数据：\n", datas[0]
    #关闭游标
    cur.close()
    #提交事务
    conn.commit()
    #关闭数据库连接
    conn.close()
    print u"sql语句执行成功！"

except Exception, e:
    print e

重置游标位置
scroll(value, mode='relative')
移动指针到参数value指定的行；
Mode = relative则表示从当前所在行前移value行
Mode=absolute表示移动到绝对位置的value行。游标索引从0开始
cursor.rownumber
返回当前游标所在位置

数据库表内容:

#coding=utf-8
import MySQLdb
#打开数据库连接
conn = MySQLdb.connect(
    host = "localhost", 
    port = 3306,
    user = "root", 
    passwd = "123456", 
    db = "python", 
    charset = "utf8") 

#使用cursor()方法获取数据库的操作游标
cursor = conn.cursor()
cursor.execute("select * from user order by id")
print u"当前游标所在位置：", cursor.rownumber

print cursor.fetchone()
print u"当前游标所在位置：", cursor.rownumber
cursor.scroll(0,mode="absolute")#移动游标到第一行
print u"当前游标所在位置：", cursor.rownumber
print cursor.fetchone()

#coding=utf-8
import MySQLdb
#打开数据库连接
conn = MySQLdb.connect(
    host = "localhost", 
    port = 3306,
    user = "root", 
    passwd = "123456", 
    db = "python", 
    charset = "utf8") 

#使用cursor()方法获取数据库的操作游标
cursor = conn.cursor()
cursor.execute("select * from user order by id")
print u"当前游标所在位置：", cursor.rownumber

res = cursor.fetchmany(5)
for value in res:
    print value

print u"当前游标所在位置：", cursor.rownumber

cursor.scroll(3,mode="relative")#游标会向前移动3，对应数据库表就是向后移动3行
print u"当前游标所在位置：", cursor.rownumber
print cursor.fetchone()