有连接，有关闭，有游标
execute() # 有SQL注入问题
增删改需要conn.commit()
fetchone fetchall # 游标
cursor.lastrowid # 最后一条的自增ID executemany以后也是最后一条
################################################
SQL注入：
import pymysql
user = input('用户名：')
pdw = input('密码：')
conn = pymysql.connect(host = 'localhost',user = 'root',password = '',database ='db666'，charset = 'utf-8')
cursor = conn.cursor()
# sql = "select * from userinfo where username = '%s' and password = '%s'"%(user,pwd)
# cursor.execute(sql) # 自己进行字符串拼接会被SQL注入
# select * from userinfo where username = 'uu' or 1=1 -- 'and password = '%s' #SQL注入
sql = "select * from userinfo where username = %s and password = %s"
cursor.execute(sql,user,pwd) # 或者][user,pwd]或者字典拼接
result = cursor.fetchone()
cursor.close()
conn.close()
if result:
print('登陆成功')
else:
print('登陆失败')
################################################
查：
import pymysql
conn = pymysql.connect(host = 'localhost',user = 'root',password = '',database ='db666'，charset = 'utf-8')
cursor = conn.cursor(cursor=pymysql.cursors.DictCursor) # 以字典形式显示，常用
sql = 'select * from userinfo'
cursor.execute(sql)
# cursor.scroll(1,mode='relative') # 相对当前位置移动
# cursor.scroll(2,mode='absolute') # 绝对位置移动
result = cursor.fetchone()
result = cursor.fetchone() # 一次取一个
result = cursor.fetchmany(4) # 取4个
result = cursor.fetchall()
cursor.close()
conn.close()
################################################
改：
import pymysql
conn = pymysql.connect(
host='localhost',
user='root',
password='',
database='db666')
cursor = conn.cursor()
sql1 = "insert into userinfo(username,password) values(%s，%s)"
data =[('egg','sb'),('alex','sb')]
try:
r = cursor.executemany(sql1,data)
print(r)# 一次提交多个，返回受影响行数
conn.commit() # 有修改操作必须commit
except Exception as e:
print("出错了！")
conn.rollback # 会把整个commit回滚
cursor.close()
conn.close()
