Python 操作 MySQL

大数据

作者:Rust Fisher

配置

  • win_64
  • Ubuntu14.04
  • Python3.x

pip安装pymysql模块

直接使用pip安装 pip install pymysql
win64上直接在cmd中执行

连接本地数据库

使用模块 pymysql 连接数据库

本地数据库相关配置请参阅: http://rustfisher.github.io/2017/02/25/backend/MySQL_install/

#!/usr/bin/python
# coding=utf-8
import pymysql

# 连接本地数据库
conn = pymysql.connect(host='localhost', port=3306, user='root', passwd='a123', db='samp_db1', charset='utf8')
cursor = conn.cursor()
cursor.execute('select * from bigstu')
for row in cursor.fetchall():
    print(row)

# 查
cursor.execute('select id, name from bigstu where age > 22')
for res in cursor.fetchall():
    print(str(res[0]) + ", " + res[1])

cursor.close()
print('-- end --')

输出:

(1, '张三', '男', 24, datetime.date(2017, 3, 29), '13666665555')
(6, '小刚', '男', 23, datetime.date(2017, 3, 11), '778899888')
(8, '小霞', '女', 20, datetime.date(2017, 3, 13), '13712345678')
(12, '小智', '男', 21, datetime.date(2017, 3, 7), '13787654321')
1, 张三
6, 小刚
-- end --

可以直接执行sql语句。获得的结果是元组。

插入数据

插入一条数据,接上面的代码

insertSql = "insert into bigstu (name, sex, age, mobile) values ('%s','%s',%d,'%s') "
xiuji = ('秀吉', '男', 15, '13400001111')
cursor.execute(insertSql % xiuji)
conn.commit() # 别忘了提交

添加列

在mobile后面添加一列cash

addCo = "alter table bigstu add cash int after mobile"
cursor.execute(addCo)

如果要设置默认值

addCo = "alter table bigstu add cash int default 0 after mobile"
cursor.execute(addCo)

删除数据

删除 name=秀吉 的数据

deleteSql = "delete from bigstu where name = '%s'"
cursor.execute(deleteSql % '秀吉')

删除列

删除cash列

dropCo = "alter table bigstu drop cash"
cursor.execute(dropCo)

修改数据

更新符合条件的数据

updateSql = "update bigstu set sex = '%s' where name = '%s'"
updateXiuji = ('秀吉', '秀吉') # 秀吉的性别是秀吉
cursor.execute(updateSql % updateXiuji)
conn.commit()

事物处理

给某个记录的cash增加

table = "bigstu"
addCash = "update " + table + " set cash = cash + '%d' where name = '%s'"
lucky = (1000, "秀吉")

try:
    cursor.execute(addCash % lucky)
except Exception as e:
    conn.rollback()
    print("加钱失败了")
else:
    conn.commit()

直接执行SQL语句,十分方便

代码片段

给数据库添加列

从json中读取需要添加的列名,获取当前2个表中所有的列名

整理得出需要插入的列名,然后将列插入到相应的表中

import pymysql
import json
import os
import secureUtils

mapping_keys = json.load(open("key_mapping_db.json", "r"))
db_keys = []  # json中所有的key

for k in mapping_keys.values():
    db_keys.append(k)

conn = pymysql.connect(host='localhost', port=3306, user='root',
                       passwd='*****', db='db_name', charset='utf8')

cursor = conn.cursor()
table_main = "table_main"
main_table_keys = []  # 主表的列名
cursor.execute("show columns from " + table_main)
for row in cursor.fetchall():
    main_table_keys.append(row[0])

staff_table_keys = []
cursor.execute("show columns from table_second")
for row in cursor.fetchall():
    staff_table_keys.append(row[0])

need_to_insert_keys = []
for k in db_keys:
    if k not in staff_table_keys and k not in main_table_keys and k not in need_to_insert_keys:
        need_to_insert_keys.append(k)

print("need to insert " + str(len(need_to_insert_keys)))
print(need_to_insert_keys)
for kn in need_to_insert_keys:
    print("add key to db " + kn)
    cursor.execute("alter table staff_table add " + kn +" text")

conn.close()

将字段字符改变

这里将main_table_keys中的所有字段改为utf8

# change column character set to utf8
for co in main_table_keys:
    change_sql = "alter table " + table_main + " modify " + co + " text character set utf8"
    print(change_sql)
    cursor.execute(change_sql)
End.

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