59、pymysql的链接和操作

1、pymysql连接

import pymysql     #导入pymysql模块

conn=pymysql.connect(           #连接mysql数据库
    host="localhost",
    port=3306,              #端口号是数据类型
    database="db1",     #本地数据库名字
    user="root",
    password="123456",
    charset="utf8"              #没有-
)
cursor=conn.cursor()               #获取输入sql语句的光标对象
sql="select * from info "             #sql语句
ret=cursor.execute(sql)                #执行sql语句
print(ret)                                             #打印
cursor.close()
conn.close()

2、pymysql连接验证登陆

user=input("请输入姓名：")
pwd=input("请输入密码：")
import pymysql
conn=pymysql.connect(
    host="localhost",
    port=3306,
    database="db1",
    user="root",
    password="123456",
    charset="utf8",
)
cursor=conn.cursor()
sql = "select * from userinfo where username = %s and password = %s"
ret=cursor.execute(sql,[user,pwd])
if ret:
    print("登陆成功")
else:
    print("登陆失败")

cursor.close()
conn.close()

3、pymysql增操作

import pymysql

conn=pymysql.connect(
    host="localhost",
    port=3306,
    database="db1",
    user="root",
    password="123456",
    charset="utf8"
)
cursor=conn.cursor()
sql="insert into userinfo(username,password) VALUES (%s,%s)"
cursor.execute(sql,['liuxing','lll'])
conn.commit()
cursor.close()
conn.close()

4、获取插入数据的id：lastrowid

import pymysql           #导入MySQL模块
conn=pymysql.connect(     #连接
    host="localhost",
    port=3306,
    database="db1",
    user='root',
    password='123456',
    charset="utf8",
)
cursor=conn.cursor()      #获取输入光标
sql1="insert into class(name) VALUES (%s)"   #sql语句
sql2="insert into student(name,cid) VALUES (%s,%s)"   #sql语句

cursor.execute(sql1,"全栈九期")    #执行sql语句
new_id=cursor.lastrowid   #获取最后插入数据的id并关联到另一个表
cursor.execute(sql2,["小东北",new_id])  #执行sql语句，把获取的id传入光标并执行

conn.commit()  #提交
cursor.close()  #关闭光标
conn.close()   #关闭链接

5、异常回滚

# 导入pymysql模块
import pymysql
# 连接database
conn = pymysql.connect(host=“你的数据库地址”, user=“用户名”,password=“密码”,database=“数据库名”,charset=“utf8”)
# 得到一个可以执行SQL语句的光标对象
cursor = conn.cursor()
sql = "INSERT INTO USER1(name, age) VALUES (%s, %s);"
username = "Alex"
age = 18
try:
    # 执行SQL语句
    cursor.execute(sql, [username, age])
    # 提交事务
    conn.commit()
except Exception as e:
    # 有异常，回滚事务
    conn.rollback()
cursor.close()
conn.close()

6、批量增操作

#批量插入操作
import pymysql

conn=pymysql.connect(
    host="localhost",
    port=3306,
    database="db1",
    user="root",
    password="123456",
    charset="utf8"
)
cursor=conn.cursor()
sql="insert into userinfo(username,password) VALUES (%s,%s)"
data=[("alex","dashabi"),("egon","xiaoshabi")]
cursor.executemany(sql,data)

conn.commit()
cursor.close()
conn.close()

7、删除

# 导入pymysql模块
import pymysql
# 连接database
conn = pymysql.connect(host=“你的数据库地址”, user=“用户名”,password=“密码”,database=“数据库名”,charset=“utf8”)
# 得到一个可以执行SQL语句的光标对象
cursor = conn.cursor()
sql = "DELETE FROM USER1 WHERE id=%s;"
try:
    cursor.execute(sql, [4])
    # 提交事务
    conn.commit()
except Exception as e:
    # 有异常，回滚事务
    conn.rollback()
cursor.close()
conn.close()

8、改

# 导入pymysql模块
import pymysql
# 连接database
conn = pymysql.connect(host=“你的数据库地址”, user=“用户名”,password=“密码”,database=“数据库名”,charset=“utf8”)
# 得到一个可以执行SQL语句的光标对象
cursor = conn.cursor()
# 修改数据的SQL语句
sql = "UPDATE USER1 SET age=%s WHERE name=%s;"
username = "Alex"
age = 80
try:
    # 执行SQL语句
    cursor.execute(sql, [age, username])
    # 提交事务
    conn.commit()
except Exception as e:
    # 有异常，回滚事务
    conn.rollback()
cursor.close()
conn.close()

9、查

# 导入pymysql模块
import pymysql
# 连接database
conn = pymysql.connect(host=“你的数据库地址”, user=“用户名”,password=“密码”,database=“数据库名”,charset=“utf8”)
# 得到一个可以执行SQL语句的光标对象
cursor = conn.cursor()
# 查询数据的SQL语句
sql = "SELECT id,name,age from USER1 WHERE id=1;"
# 执行SQL语句
cursor.execute(sql)
# 获取单条查询数据
ret = cursor.fetchone()
cursor.close()
conn.close()
# 打印下查询结果
print(ret)

10、查询多条语句

# 导入pymysql模块
import pymysql
# 连接database
conn = pymysql.connect(host=“你的数据库地址”, user=“用户名”,password=“密码”,database=“数据库名”,charset=“utf8”)
# 得到一个可以执行SQL语句的光标对象
cursor = conn.cursor()
# 查询数据的SQL语句
sql = "SELECT id,name,age from USER1;"
# 执行SQL语句
cursor.execute(sql)
# 获取多条查询数据
ret = cursor.fetchall()
cursor.close()
conn.close()
# 打印下查询结果
print(ret)

11、补充

# 可以获取指定数量的数据
cursor.fetchmany(3)
# 光标按绝对位置移动1
cursor.scroll(1, mode="absolute")
# 光标按照相对位置(当前位置)移动1
cursor.scroll(1, mode="relative")