Python使用pymysql模块操作mysql增删改查实例分析

# -*- coding:utf-8 -*-
import pymysql
user = input('请输入用户名：')
pwd = input('请输入密码：')
# 1.连接
conn = pymysql.connect(host='127.0.0.1', port=3306, user='root', password='123', db='t1', charset='utf8')
print(conn)
# 2.创建游标
cursor = conn.cursor()
#注意%s需要加引号
sql = "select * from t1.userinfo where username='%s' and pwd='%s'" %(user, pwd)
print(sql)
# 3.执行sql语句
cursor.execute(sql)
result=cursor.execute(sql) #执行sql语句，返回sql查询成功的记录数目
print(result)
# 关闭连接，游标和连接都要关闭
cursor.close()
conn.close()
if result:
 print('登陆成功')
else:
 print('登录失败')

# 原来是我们对sql进行字符串拼接
# sql="select * from userinfo where name='%s' and password='%s'" %(username,pwd)
# print(sql)
# result=cursor.execute(sql)
#改写为（execute帮我们做字符串拼接，我们无需且一定不能再为%s加引号了）
sql="select * from userinfo where name=%s and pwd=%s" #！！！注意%s需要去掉引号，因为pymysql会自动为我们加上
result=cursor.execute(sql,[user,pwd]) #pymysql模块自动帮我们解决sql注入的问题，只要我们按照pymysql的规矩来。

# -*- coding:utf-8 -*-
import pymysql
user = input('请输入用户名').strip()
pwd = input('请输入密码').strip()
# 连接服务端
conn = pymysql.connect(
 host='127.0.0.1',
 user='root',
 password="123",
 database='t1',
 port=3306,
 charset='utf8'
)
# -- ddadad
# 创建游标对象
cur = conn.cursor()
sql = "select * from userinfo where username = %(name)s and pwd = %(password)s"
print(sql)
# resultNum = cur.execute(sql,[user,pwd])
resultNum = cur.execute(sql,{"name":user,"password":pwd})
print(resultNum)
cur.close()
conn.close()
if resultNum:
 print('登陆成功')
else:
 print('登陆失败')

import pymysql
username = input('请输入用户名：')
pwd = input('请输入密码：')
# 1.连接
conn = pymysql.connect(host='localhost', port=3306, user='root', password='123', db='db8', charset='utf8')
# 2.创建游标
cursor = conn.cursor()
--------增删改操作----------------
#一定记得commit
conn.commit()
# 4.关闭游标
cursor.close()
# 5.关闭连接
conn.close()

sql='insert into userinfo(username,pwd) values(%s,%s)'
effect_row=cursor.execute(sql,(username,pwd)) # effect_row=1

sql='insert into userinfo(username,pwd) values(%s,%s)'
effect_row=cursor.executemany(sql,[('赵八','112'),('刘九','114'),('封十','911')]) #effect_row=3

sql='delete from userinfo where pwd like "%2"'
effect_row=cursor.execute(sql)

sql='update userinfo set username = %s where pwd="114"'
effect_row=cursor.execute(sql,'niu') #effect_row=2

mysql> select * from userinfo;
+----+----------+-----+
| id | username | pwd |
+----+----------+-----+
| 1 | mjj  | 123 |
| 3 | 张三  | 110 |
| 4 | 李四  | 119 |
+----+----------+-----+
3 rows in set (0.00 sec)

import pymysql
# 1.连接
conn = pymysql.connect(host='localhost', port=3306, user='root', password='', db='db8', charset='utf8')
# 2.创建游标
cursor = conn.cursor()
sql = 'select * from userinfo'
cursor.execute(sql)
------------执行的查询--------------
# 4.关闭游标
cursor.close()
# 5.关闭连接
conn.close()

# 查询第一行的数据
row = cursor.fetchone()
print(row) # (1, 'mjj', '123')
# 查询第二行数据
row = cursor.fetchone()
print(row) # (3, '张三', '110')

# 获取所有的数据
rows = cursor.fetchall()
print(rows)
#运行结果
((1, 'mjj', '123'), (3, '张三', '110'), (4, '李四', '119')) 取到的返回值是元组

row=cursor.fetchmany(3)
print(row)

cursor.scroll(1,mode='relative') # 相对当前位置移动
cursor.scroll(2,mode='absolute') # 相对绝对位置移动

# 查询第一行的数据
row = cursor.fetchone()
print(row) # (1, 'mjj', '123')
# 查询第二行数据
row = cursor.fetchone() # (3, '张三', '110')
print(row)
cursor.scroll(-1,mode='relative') #设置之后，光标相对于当前位置往前移动了一行，所以打印的结果为第二行的数据
row = cursor.fetchone()
print(row)
cursor.scroll(0,mode='absolute') #设置之后，光标相对于首行没有任何变化，所以打印的结果为第一行数据
row = cursor.fetchone()
print(row)