python 查询数据库返回格式学习

一、返回tuple元组类型（默认）

fetchall()将结果放在二维数组里面，每一行的结果在元组里面

import pymysql
def export(table_name):
    conn =pymysql.connect(host = '118.24.3.40',
                          user = 'jxz',password='123456',
                          db='jxz',port=3306,charset = 'utf8')
    cur = conn.cursor()
    cur.execute('select * from %s'%table_name)
    print(cur.fetchall())
export('app_student')

二、返回字典类型

想返回字典格式，只需要在建立游标的时候加个参数，cursor=pymysql.cursors.DictCursor。这样每行返回的值放在字典里面，然后整体放在一个list里面。

import pymysql
def export(table_name):
    conn =pymysql.connect(host = '118.24.3.40',
                          user = 'jxz',password='123456',
                          db='jxz',port=3306,charset = 'utf8')
    cur = conn.cursor(cursor=pymysql.cursors.DictCursor)
    cur.execute('select * from %s'%table_name)
    print(cur.fetchall())
export('app_student')

三、返回list类型

使用list(chain.from_iterable(elems))

from itertools import chain

sql="select elems from table"
cursor.execute(sql)
elems = cursor.fetchall()
resultlist = list(chain.from_iterable(elems))