pymysql怎么操作mysql数据库

1、pymysql.connent

conn = pymysql.connect(host='127.0.0.1', 
                 port=3306, user='root', passwd='@123456', db='db4')

2、conn.cursor()

cursor = conn.cursor()

# 游标设置为字典类型
cursor = conn.cursor("cursor"=pymysql.cursors.DictCursor)
栗子：
sql = "select * from department;"
# 执行sql语句的函数,使用下面函数进行拼接,防止SQL注入
cursor.execute(sql)
# cursor.scroll(1,mode='relative')
result = cursor.fetchone()
print(result)
输出结果：
{'id': 1, 'title': '财务'}

3、cursor.execute()

cursor.execute(sql)

4、cursor.executemany()

cursor.executemany(sql,[('销售'), ('经理')])

5、cursor.fetchone()

import  pymysql
# 创建链接，跟socket服务类似
conn = pymysql.connect(host='127.0.0.1', port=3306, 
                 user='root', passwd='@123456', db='db4')
# 创建游标(相当与创建一个拿数据的手)
cursor = conn.cursor()
# 创建要执行的SQL语句
sql = "select * from department;"
# 执行sql语句的函数,使用下面函数进行拼接,防止SQL注入
cursor.execute(sql)
result = cursor.fetchone()
print(result)
result = cursor.fetchone()
print(result)
result = cursor.fetchone()
print(result)
# 关闭链接
cursor.close()
conn.close()
·
输出结果：
(1, '财务')
(2, '公关')
(3, '测试')

6、cursor.scroll()

1、
cursor.execute(sql)
result = cursor.fetchone()
print(result)
输出结果：
(1, '财务')
2、
cursor.execute(sql)
cursor.scroll(1,mode='absolute')
result = cursor.fetchone()
print(result)
输出结果：
(2, '公关')
3、
cursor.execute(sql)
cursor.scroll(1,mode='relative')
result = cursor.fetchone()
print(result)
输出结果：
(2, '公关')

7、cursor.fetchmany()

cursor.execute(sql)
# cursor.scroll(1,mode='relative')
# result = cursor.fetchone()
# print(result)
result = cursor.fetchmany(2)
print(result)
输出结果：
((1, '财务'), (2, '公关'))

8、cursor.fetchall()

sql = "select * from department;"
# 执行sql语句的函数,使用下面函数进行拼接,防止SQL注入
cursor.execute(sql)
# cursor.scroll(1,mode='relative')
# result = cursor.fetchone()
# print(result)
# result = cursor.fetchmany(2)
# print(result)
result = cursor.fetchall()
print(result)
输出结果：
((1, '财务'), (2, '公关'), (3, '测试'), (4, '运维'), (5, '销售'))

9、cursor.lastrowid()

sql = "insert into department(title) values(%s)"
cursor.executemany(sql,[('经理')])
# 获取插入值的自增id
print(cursor.lastrowid)
# 将执行的结果提交到表中，否则表不会发生变换
conn.commit()
输出结果：
6

10、今日练习

【1、创建权限表】
CREATE TABLE power (
	pid INT auto_increment PRIMARY KEY,
	purview	CHAR(10)
)ENGINE= INNODB DEFAULT CHARSET= utf8;
【2、创建用户表】
CREATE TABLE users (
	uid INT auto_increment PRIMARY KEY,
	username	CHAR(10)
)ENGINE= INNODB DEFAULT CHARSET= utf8;
【3、创建用户权限关系表】
CREATE TABLE use_pow (
	upid INT auto_increment PRIMARY KEY,
	power_id INT,
	user_id INT,
	UNIQUE uq_pid_uid(power_id, user_id),
	CONSTRAINT fk_pow FOREIGN KEY (power_id) REFERENCES power(pid),
	CONSTRAINT fk_user FOREIGN KEY (user_id) REFERENCES users(uid)
)ENGINE= INNODB DEFAULT CHARSET= utf8;
py文件：
import pymysql
user = input('请输入用户名称>>>')
# 连接数据库
conn  = pymysql.connect(host='127.0.0.1', port=3306, 
                  user='root', passwd='@123456', db='db_grant')
# 创建光标
cursor = conn.cursor()
# 查询是否存在该用户
sql = "SELECT uid FROM users WHERE username = %(u)s"
cursor.execute(sql, {'u': user})
# 获取到用户的id
uid = cursor.fetchone()
# print(uid[0], type(uid[0]))
if uid:
# 这里的%s如果换成%d就会报错因为execute无论传入什么类型都要用%s来占位
sql2 = "SELECT purview from power WHERE pid in 
(SELECT power_id FROM use_pow WHERE user_id = %s)"
cursor.execute(sql2, uid[0])
result = cursor.fetchall()
print(result)
else:
print("没有该用户")
cursor.close()
conn.close()