python 操作数据库的常用SQL命令

这俩天在学习PYTHON操作数据库的知识。其实基本SQL命令是与以前学习的MYSQL命令一致，只是增加了一些PYTHON语句。

1，安装pymysql,并导入。

import pymysql

2,因为用的就python2,所以加上一步。

import sys
reload(sys)
sys.setdefaultencoding('gb18030')

3，因为我已经在本地下载了mysql数据库，并新建了表。
所以这一步，我就直接连接本地的数据库就可以了。
conn=pymysql.connect(host='127.0.0.1',user='root',password='123456',db='caipiao')  ###这里我是连接的本地数据库，没有写端口号3306，数据库名称：caipiao,用户是root,
cur=conn.cursor()
###这里就是我们要进行的操作步骤，先空着。####
conn.commit()
cur.close()

##################################################下面来讲一下常用的SQL命令#####################################
1，插入数据：(表名也是：caipiao)

conn=pymysql.connect(host='127.0.0.1',user='root',password='123456',db='caipiao') 
cur=conn.cursor()
re=cur.execute("insert into caipiao values(1,'baozi',1,1),(2,'mantou',2,2),(3,'youtiao',3,3)")
conn.commit()
cur.close()
conn.close()
print (re)
现在我们可以访问我们本地的数据库，可以发现我们已经成功插入了三条数据。（id=1,name='baozi',touzhu=1,yingli=1）(*******)(******)

2,查询数据：

conn=pymysql.connect(host='127.0.0.1',user='root',password='123456',db='caipiao') 
cur=conn.cursor()
cur.execute("select* from caipiao")
ret1=cur.fetchall()   ####把查询到的数据都显示出来。
print (ret1)

ret2=cur.fetchmany(3)   ###获取表中前3条数据并打印出来
print (ret2)    

ret3=cur.fetchone()   ###获取表中第一行数据并打印出来
print (ret3)

conn.commit()
cur.close()
conn.close()

3,删除数据

conn=pymysql.connect(host='127.0.0.1',user='root',password='123456',db='caipiao') 
cur=conn.cursor()
cur.execute("delete from caipiao where id=1")
conn.commit()
cur.close()
conn.close()

4,更改数据

conn=pymysql.connect(host='127.0.0.1',user='root',password='123456',db='caipiao') 
cur=conn.cursor()
cur.execute("update caipiao set name='doujiang' where id=2")
conn.commit()
cur.close()
conn.close()

5,fetch数据类型 (关于默认获取的数据是元祖类型，如果想要字典类型的数据)

conn=pymysql.connect(host='127.0.0.1',user='root',password='123456',db='caipiao') 
cur=conn.cursor(cursor=pymysql.cursors.DictCursor)
cur.execute("select* from caipiao")
re=cur.fetchall()
print (re)
打印出来就是：###

[{u'touzhu': '10', u'caizhong': 'chongqingshishicai', u'yingli': '10', u'id': 3, u'name': 'baozi'}, {u'touzhu': '10', u'caizhong': 'chongqingxingyun', u'yingli': '20', u'id': 4, u'name': 'youtiao'}, {u'touzhu': '10', u'caizhong': 'xinjiangshishicai', u'yingli': '30', u'id': 5, u'name': 'mayuan'}, {u'touzhu': '10', u'caizhong': 'dafashishicai', u'yingli': '40', u'id': 6, u'name': 'mianbao'}, {u'touzhu': '10', u'caizhong': 'jilinkuaisan', u'yingli': '50', u'id': 7, u'name': 'changfen'}, {u'touzhu': '10', u'caizhong': 'anhuikuaisan', u'yingli': '60', u'id': 8, u'name': 'bingan'}, {u'touzhu': '10', u'caizhong': 'dafashishicai', u'yingli': '50', u'id': 9, u'name': 'mianbao'}, {u'touzhu': '10', u'caizhong': 'beijingsaiche', u'yingli': '20', u'id': 2, u'name': 'baozi'}, {u'touzhu': '11', u'caizhong': 'chongqingshishicai', u'yingli': '11', u'id': 7, u'name': 'yiyi'}, {u'touzhu': '12', u'caizhong': 'dafakuaisan', u'yingli': '12', u'id': 8, u'name': 'xiha'}, {u'touzhu': '11', u'caizhong': 'dafa1', u'yingli': '12', u'id': 8, u'name': 'man1'}, {u'touzhu': '12', u'caizhong': 'dafa2', u'yingli': '13', u'id': 9, u'name': 'man2'}, {u'touzhu': '11', u'caizhong': 'dafa1', u'yingli': '12', u'id': 8, u'name': 'man1'}, {u'touzhu': '12', u'caizhong': 'dafa2', u'yingli': '13', u'id': 9, u'name': 'man2'}, {u'touzhu': '11', u'caizhong': 'dafa1', u'yingli': '12', u'id': 8, u'name': 'man1'}, {u'touzhu': '12', u'caizhong': 'dafa2', u'yingli': '13', u'id': 9, u'name': 'man2'}, {u'touzhu': '11', u'caizhong': 'dafa1', u'yingli': '12', u'id': 8, u'name': 'man1'}, {u'touzhu': '12', u'caizhong': 'dafa2', u'yingli': '13', u'id': 9, u'name': 'man2'}, {u'touzhu': '11', u'caizhong': 'dafa1', u'yingli': '12', u'id': 8, u'name': 'man1'}, {u'touzhu': '12', u'caizhong': 'dafa2', u'yingli': '13', u'id': 9, u'name': 'man2'}]

######

conn.commit()

cur.close()

conn.close()