Python_pymysql+游标（cursor()）的应用

pymysql的应用

一、装包(前提)

py -m pip install pymysql;

 

D:\Python36\python.exe -m pip install pymysql

二、创建连接+游标的应用

1、简单示例

#coding=utf-8

import pymysql

# 打开数据库连接
conn = pymysql.connect( host = "127.0.0.1", port = 3306, user = "root", passwd = "1234qwer", db = "gloryroad", charset = "utf8") # 使用cursor()方法获取数据库的操作游标 cursor = conn.cursor() print(cursor) print(type(cursor))

2、创建数据库

try:
    conn = pymysql.connect(
    host = "127.0.0.1",
    port = 3306,
    user = "root",
    passwd = "1234qwer"
    )
    cur = conn.cursor()
    cur.execute("CREATE DATABASE IF NOT EXISTS grdb DEFAULT CHARSET utf8 COLLATE utf8_general_ci;")
    cur.close()
    conn.close()
    print("创建数据库pythonDB成功! ")
except pymysql.Error as e:
    print("Mysql Error %d: %s" %(e.args[0],e.args[1]))

 

#COLLATE utf8_general_ci：大小写不敏感

3、创建表

#coding=utf-8

import pymysql
try:
    conn = pymysql.connect(
    host = "127.0.0.1",
    port = 3306,
    user = "root",
    passwd = "1234qwer")

    conn.select_db('grdb')# 选择pythonDB数据库
    cur = conn.cursor()# 获取游标
    #如果所建表已存在，删除重建
    #cur.execute("drop table if exists User;")
    #执行建表sql语句
    cur.execute('''CREATE TABLE User (id int(11) DEFAULT NULL,name varchar(255) DEFAULT NULL,password varchar(255) DEFAULT NULL,birthday date DEFAULT NULL)ENGINE=innodb DEFAULT CHARSET=utf8;''')
    cur.close()
    conn.close()
    print(u"创建数据表成功")
except pymysql.Error as e:
    print("Mysql Error %d: %s" %(e.args[0],e.args[1]))

4、插入表数据

#coding=utf-8
import pymysql

conn = pymysql.connect(
host = "127.0.0.1",
port = 3306,
user = "root",
passwd = "1234qwer",
db = "grdb",
charset = "utf8")
#使用cursor()方法获取数据库的操作游标
cursor = conn.cursor()
#插入一条数据
insert = cursor.execute("insert into user values(1,'Tom','123','1990-01-01')")
print(u"添加语句受影响的行数：",insert)

#另一种插入数据方法，通过格式字符串传入值，此方式可以防止sql注入
sql = "insert into user values(%s,%s,%s,%s)"
insert = cursor.execute(sql,(3,'lucy','efg','1993-02-01'))
print(u"添加语句受影响的行数：",insert)
#关闭游标
cursor.close()
#提交事务
conn.commit()
# 关闭数据库连接
conn.close()
print(u"sql语句执行成功！")

5、插入数据（含字符串拼接实例）

#coding=utf-8
import pymysql

conn = pymysql.connect(
host = "127.0.0.1",
port = 3306,
user = "root",
passwd = "1234qwer",
db = "grdb",
charset = "utf8")
# 使用cursor()方法获取数据库的操作游标
cursor = conn.cursor()
# 插入一条数据
#insert = cursor.execute("insert into user values(1,'Tom','123','1990-01-01')")
#print(u"添加语句受影响的行数：", insert)

# 另一种插入数据方法，通过格式字符串传入值，此方式可以防止sql注入
sql = "insert into user values(%s,%s,%s,%s)"
j=0
for i in range(100,201):
    insert = cursor.execute(sql,(i,'lucy'+str(i),'efg'+str(i),str(1900+j)+'-02-01'))
    j+=1

# 关闭游标
cursor.close()
# 提交事务
conn.commit()#提交事务后，不能回滚了
# 关闭数据库连接
conn.close()
print(u"sql语句执行成功！")

6、查询表数据语句

6.1逐条获取cursor.fetchone

#coding=utf-8
import pymysql

import pymysql

conn = pymysql.connect(
host = "127.0.0.1",
port = 3306,
user = "root",
passwd = "1234qwer",
db = "grdb",
charset = "utf8")
# 使用cursor()方法获取数据库的操作游标
cursor = conn.cursor()
cursor.execute("select * from user")
while 1:
    res = cursor.fetchone()
    if res is None:
    # 表示已经取完结果集
        break
    print(res)
    #将读取到的时间格式化
    # print(res[-1].strftime("%Y-%m-%d"))
# 关闭游标
cursor.close()
# 提交事务
conn.commit()
# 关闭数据库连接
conn.close()
print("sql语句执行成功！")

 

#cursor.fetchone  一条一条取数据,每条数据是元祖

6.2获取n条数据

import pymysql

conn = pymysql.connect(
host = "127.0.0.1",
port = 3306,
user = "root",
passwd = "1234qwer",
db = "grdb",
charset = "utf8")
# 使用cursor()方法获取数据库的操作游标
cursor = conn.cursor()
cursor.execute("select * from user")

# 获取游标处两条数据
resTuple = cursor.fetchmany(2)
print("结果集类型：",type(resTuple))
for i in resTuple:
    print(i)
# 关闭游标
cursor.close()
# 提交事务
conn.commit()
# 关闭数据库连接
conn.close()
print("sql语句执行成功！")

7、更新数据

批量更新数据
#批量更新的代码
import pymysql

conn = pymysql.connect(
host = "127.0.0.1",
port = 3306,
user = "root",
passwd = "1234qwer",
db = "grdb",
charset = "utf8")
# 使用cursor()方法获取数据库的操作游标
cursor = conn.cursor()

#查询一条数据
query = cursor.execute("select * from user")
print("表中所有数据：")
for i in cursor.fetchall():
  print(i)
# 批量更新数据
cursor.executemany("update user set password = %s where name=%s",
[('tomx2x', 'tom'), ('Tomx2x', 'amy')])
# 查看更新后的结果
query = cursor.execute("select * from user where name='tom' or name='amy'")
print("表中所有数据：")
for i in cursor.fetchall():
  print(i)
# 关闭游标
cursor.close()
# 提交事务
conn.commit()
# 关闭数据库连接
conn.close()
print("sql语句执行成功！")

8、删除数据

import pymysql

conn = pymysql.connect(
host = "127.0.0.1",
port = 3306,
user = "root",
passwd = "1234qwer",
db = "grdb",
charset = "utf8")
# 使用cursor()方法获取数据库的操作游标
cursor = conn.cursor()

cursor.execute("select * from user")
print("表中所有数据：")
for i in cursor.fetchall():
    print(i)
# 删除数据
delete = cursor.execute("delete from user where name='tom'")
print("删除语句影响的行数：",delete)

print("删除一条数据后，表中数据：")
cursor.execute("select * from user")
for i in cursor.fetchall():
    print(i)

# 关闭游标
cursor.close()
# 提交事务
conn.commit()
# 关闭数据库连接
conn.close()
print("sql语句执行成功！")
cursor.close()

9、回滚事务（roll back）

回滚事务