MYSQL进阶 - 爱码网

pymsql是Python中操作MySQL的模块，其使用方法和py2的MySQLdb几乎相同。

模块安装

1	`pip install pymysql`

执行sql语句

import pymysql
#添加数据


conn = pymysql.connect(host='127.0.0.1', port=3306, user='root', passwd='', db='yyy')
cursor = conn.cursor()
# sql = """CREATE TABLE EMPLOYEE (

          FIRST_NAME  CHAR(20) NOT NULL,


          LAST_NAME  CHAR(20),


          AGE INT,


          SEX CHAR(1),


          INCOME FLOAT )"""



 cursor.execute(sql)
#row_affected = cursor.execute("create table t1(id INT ,name VARCHAR(20))")
#row_affected=cursor.execute("INSERT INTO t1(id,name) values (1,'alvin'),(2,'xialv')")
#cursor.execute("update t1 set name = 'silv2' where id=2")
#查询数据

row_affected=cursor.execute("select * from t1")

one=cursor.fetchone()
# many=cursor.fetchmany(2)
 all=cursor.fetchall()
#scroll
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
#更改获取数据结果的数据类型,默认是元组,可以改为字典等:conn.cursor(cursor=pymysql.cursors.DictCursor)

conn.commit()

cursor.close()

conn.close()

回到顶部

事务

事务命令

事务指逻辑上的一组操作，组成这组操作的各个单元，要不全部成功，要不全部不成功。

数据库开启事务命令

--        start transaction 开启事务
--        Rollback 回滚事务,即撤销指定的sql语句(只能回退insert delete update语句)，回滚到上一次commit的位置
--        Commit 提交事务，提交未存储的事务
-- 
--        savepoint 保留点 ，事务处理中设置的临时占位符 你可以对它发布回退(与整个事务回退不同)

转账实例：

1 2	`UPDATE` `account` `set` `balance=balance-5000` `WHERE` `name=”yuan”;` `UPDATE` `account` `set` `balance=balance+5000` `WHERE` `name=”xialv”;`

create table test2(id int PRIMARY KEY auto_increment,name VARCHAR(20)) engine=innodb;
INSERT INTO test2(name) VALUE ("alvin"),
                              ("yuan"),
                              ("xialv");
start transaction;
insert into test2 (name)values('silv');
select * from test2;
commit;
-- 保留点


start transaction;
insert into test2 (name)values('wu');

savepoint insert_wu;
select * from test2;
delete from test2 where id=4;

savepoint delete1;
select * from test2;
delete from test2 where id=1;

savepoint delete2;
select * from test2;
rollback to delete1;
select * from test2;

savepoint

python中调用数据库启动事务的方式

import pymysql
添加数据
conn = pymysql.connect(host='127.0.0.1', port=3306, user='root', passwd='', db='yyy')
cursor = conn.cursor()
try:

insertSQL0="INSERT INTO ACCOUNT2 (name,balance) VALUES ('oldboy',4000)"

insertSQL1="UPDATE account2 set balance=balance-30 WHERE name='yuan'"

insertSQL2="UPDATE account2 set balance=balance+30 WHERE name='xialv'"
</span><span style="color: #0000ff;">cursor</span> <span style="color: #808080;">=</span> conn.<span style="color: #0000ff;">cursor</span><span style="color: #000000;">()

</span><span style="color: #0000ff;">cursor</span>.<span style="color: #0000ff;">execute</span><span style="color: #000000;">(insertSQL0)
conn.</span><span style="color: #0000ff;">commit</span><span style="color: #000000;">()

</span><span style="color: #0000ff;">cursor</span>.<span style="color: #0000ff;">execute</span><span style="color: #000000;">(insertSQL1)
raise Exception
</span><span style="color: #0000ff;">cursor</span>.<span style="color: #0000ff;">execute</span><span style="color: #000000;">(insertSQL2)
</span><span style="color: #0000ff;">cursor</span>.<span style="color: #0000ff;">close</span><span style="color: #000000;">()
conn.</span><span style="color: #0000ff;">commit</span><span style="color: #000000;">()

except Exception as e:
conn.</span><span style="color: #0000ff;">rollback</span><span style="color: #000000;">()
conn.</span><span style="color: #0000ff;">commit</span><span style="color: #000000;">()

cursor.close()

conn.close()

View Code