利用python模拟sql语句对员工表格进行增删改查

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具体需求:

员工信息表程序，实现增删改查操作：

可进行模糊查询，语法支持下面3种:

select name,age from staff_data where age > 22                  多个查询参数name,age 用','分割

select * from staff_data where dept = 人事

select * from staff_data where enroll_date like 2013

查到的信息，打印后，最后面还要显示查到的条数

可创建新员工纪录，以phone做唯一键，phone存在即提示,staff_id需自增,添加多个记录record1/record2中间用'/'分割

insert into staff_data values record1/record2

可删除指定员工信息纪录，输入员工id，即可删除

delete from staff_data where staff_id>=5andstaff_id<=10

可修改员工信息，语法如下:

update staff_table set dept=Market,phone=13566677787  where dept = 运维   多个set值用','分割

使用re模块,os模块,充分使用函数精简代码,熟练使用 str.split()来解析格式化字符串

由于,sql命令中的几个关键字符串有一定规律,只出现一次,并且有顺序!!!

按照key_lis = ['select', 'insert', 'delete', 'update', 'from', 'into', 'set', 'values', 'where', 'limit']的元素顺序分割sql. 

分割元素作为sql_dic字典的key放进字典中.分割后的列表为b,如果len(b)>1,说明sql字符串中含有分割元素,同时b[0]对应上一个分割元素的值,b[-1]为下一次分割对象!

这样不断迭代直到把sql按出现的所有分割元素分割完毕,但注意这里每次循环都是先分割后赋值!!!当前分割元素比如'select'对应的值,需要等到下一个分割元素

比如'from'执行分割后的列表b,其中b[0]的值才会赋值给sql_dic['select'] ,所以最后一个分割元素的值,不能通过上述循环来完成,必须先处理可能是最后一个分割元素,再正常循环!!

在这sql语句中,有可能成为最后一个分割元素的 'limit' ,'values', 'where',  按优先级别,先处理'limit' ,再处理'values'或 'where'.....

处理完得到sql_dic后,就是你按不同命令执行,对数据文件的增删改查,最后返回处理结果!!

示例代码

# _*_coding:utf-8_*_
# Author:Jaye He
import re
import os


def sql_parse(sql, key_lis):
 '''
 解析sql命令字符串,按照key_lis列表里的元素分割sql得到字典形式的命令sql_dic
 :param sql:
 :param key_lis:
 :return:
 '''
 sql_list = []
 sql_dic = {}
 for i in key_lis:
  b = [j.strip() for j in sql.split(i)]
  if len(b) > 1:
   if len(sql.split('limit')) > 1:
    sql_dic['limit'] = sql.split('limit')[-1]
   if i == 'where' or i == 'values':
    sql_dic[i] = b[-1]
   if sql_list:
    sql_dic[sql_list[-1]] = b[0]
   sql_list.append(i)
   sql = b[-1]
  else:
   sql = b[0]
  if sql_dic.get('select'):
   if not sql_dic.get('from') and not sql_dic.get('where'):
    sql_dic['from'] = b[-1]
 if sql_dic.get('select'):
  sql_dic['select'] = sql_dic.get('select').split(',')
 if sql_dic.get('where'):
  sql_dic['where'] = where_parse(sql_dic.get('where'))
 return sql_dic


def where_parse(where):
 '''
 格式化where字符串为列表where_list,用'and', 'or', 'not'分割字符串
 :param where:
 :return:
 '''
 casual_l = [where]
 logic_key = ['and', 'or', 'not']
 for j in logic_key:
  for i in casual_l:
   if i not in logic_key:
    if len(i.split(j)) > 1:
     ele = i.split(j)
     index = casual_l.index(i)
     casual_l.pop(index)
     casual_l.insert(index, ele[0])
     casual_l.insert(index+1, j)
     casual_l.insert(index+2, ele[1])
     casual_l = [k for k in casual_l if k]
 where_list = three_parse(casual_l, logic_key)
 return where_list


def three_parse(casual_l, logic_key):
 '''
 处理临时列表casual_l中具体的条件,'staff_id>5'-->['staff_id','>','5']
 :param casual_l:
 :param logic_key:
 :return:
 '''
 where_list = []
 for i in casual_l:
  if i not in logic_key:
   b = i.split('like')
   if len(b) > 1:
    b.insert(1, 'like')
    where_list.append(b)
   else:
    key = ['<', '=', '>']
    new_lis = []
    opt = ''
    lis = [j for j in re.split('([=<>])', i) if j]
    for k in lis:
     if k in key:
      opt += k
     else:
      new_lis.append(k)
    new_lis.insert(1, opt)
    where_list.append(new_lis)
  else:
   where_list.append(i)
 return where_list


def sql_action(sql_dic, title):
 '''
 把解析好的sql_dic分发给相应函数执行处理
 :param sql_dic:
 :param title:
 :return:
 '''
 key = {'select': select,
   'insert': insert,
   'delete': delete,
   'update': update}
 res = []
 for i in sql_dic:
  if i in key:
   res = key[i](sql_dic, title)
 return res


def select(sql_dic, title):
 '''
 处理select语句命令
 :param sql_dic:
 :param title:
 :return:
 '''
 with open('staff_data', 'r', encoding='utf-8') as fh:
  filter_res = where_action(fh, sql_dic.get('where'), title)
  limit_res = limit_action(filter_res, sql_dic.get('limit'))
  search_res = search_action(limit_res, sql_dic.get('select'), title)
 return search_res


def insert(sql_dic, title):
 '''
 处理insert语句命令
 :param sql_dic:
 :param title:
 :return:
 '''
 with open('staff_data', 'r+', encoding='utf-8') as f:
  data = f.readlines()
  phone_list = [i.strip().split(',')[4] for i in data]
  ins_count = 0
  if not data:
   new_id = 1
  else:
   last = data[-1]
   last_id = int(last.split(',')[0])
   new_id = last_id+1
  record = sql_dic.get('values').split('/')
  for i in record:
   if i.split(',')[3] in phone_list:
    print('\033[1;31m%s 手机号已存在\033[0m' % i)
   else:
    new_record = '%s,%s\n' % (str(new_id), i)
    f.write(new_record)
    new_id += 1
    ins_count += 1
  f.flush()
 return ['insert successful'], [str(ins_count)]


def delete(sql_dic, title):
 '''
 处理delete语句命令
 :param sql_dic:
 :param title:
 :return:
 '''
 with open('staff_data', 'r', encoding='utf-8') as r_file,\
   open('staff_data_bak', 'w', encoding='utf-8') as w_file:
  del_count = 0
  for line in r_file:
   dic = dict(zip(title.split(','), line.split(',')))
   filter_res = logic_action(dic, sql_dic.get('where'))
   if not filter_res:
    w_file.write(line)
   else:
    del_count += 1
  w_file.flush()
 os.remove('staff_data')
 os.rename('staff_data_bak', 'staff_data')
 return ['delete successful'], [str(del_count)]


def update(sql_dic, title):
 '''
 处理update语句命令
 :param sql_dic:
 :param title:
 :return:
 '''
 set_l = sql_dic.get('set').strip().split(',')
 set_list = [i.split('=') for i in set_l]
 update_count = 0
 with open('staff_data', 'r', encoding='utf-8') as r_file,\
   open('staff_data_bak', 'w', encoding='utf-8') as w_file:
  for line in r_file:
   dic = dict(zip(title.split(','), line.strip().split(',')))
   filter_res = logic_action(dic, sql_dic.get('where'))
   if filter_res:
    for i in set_list:
     k = i[0]
     v = i[-1]
     dic[k] = v
    line = [dic[i] for i in title.split(',')]
    update_count += 1
    line = ','.join(line)+'\n'
   w_file.write(line)
  w_file.flush()
 os.remove('staff_data')
 os.rename('staff_data_bak', 'staff_data')
 return ['update successful'], [str(update_count)]


def where_action(fh, where_list, title):
 '''
 具体处理where_list里的所有条件
 :param fh:
 :param where_list:
 :param title:
 :return:
 '''
 res = []
 if len(where_list) != 0:
  for line in fh:
   dic = dict(zip(title.split(','), line.strip().split(',')))
   if dic['name'] != 'name':
    logic_res = logic_action(dic, where_list)
    if logic_res:
     res.append(line.strip().split(','))
 else:
  res = [i.split(',') for i in fh.readlines()]
 return res
 pass


def logic_action(dic, where_list):
 '''
 判断数据文件中每一条是否符合where_list条件
 :param dic:
 :param where_list:
 :return:
 '''
 logic = []
 for exp in where_list:
  if type(exp) is list:
   exp_k, opt, exp_v = exp
   if exp[1] == '=':
    opt = '=='
   logical_char = "'%s'%s'%s'" % (dic[exp_k], opt, exp_v)
   if opt != 'like':
    exp = str(eval(logical_char))
   else:
    if exp_v in dic[exp_k]:
     exp = 'True'
    else:
     exp = 'False'
  logic.append(exp)
 res = eval(' '.join(logic))
 return res


def limit_action(filter_res, limit_l):
 '''
 用列表切分处理显示符合条件的数量
 :param filter_res:
 :param limit_l:
 :return:
 '''
 if limit_l:
  index = int(limit_l[0])
  res = filter_res[:index]
 else:
  res = filter_res
 return res


def search_action(limit_res, select_list, title):
 '''
 处理需要查询并显示的title和相应数据
 :param limit_res:
 :param select_list:
 :param title:
 :return:
 '''
 res = []
 fields_list = title.split(',')
 if select_list[0] == '*':
  res = limit_res
 else:
  fields_list = select_list
  for data in limit_res:
   dic = dict(zip(title.split(','), data))
   r_l = []
   for i in fields_list:
    r_l.append((dic[i].strip()))
   res.append(r_l)
 return fields_list, res


if __name__ == '__main__':
 with open('staff_data', 'r', encoding='utf-8') as f:
  title = f.readline().strip()
 key_lis = ['select', 'insert', 'delete', 'update', 'from', 'into', 'set', 'values', 'where', 'limit']
 while True:
  sql = input('请输入sql命令,退出请输入exit:').strip()
  sql = re.sub(' ', '', sql)
  if len(sql) == 0:continue
  if sql == 'exit':break
  sql_dict = sql_parse(sql, key_lis)
  fields_list, fields_data = sql_action(sql_dict, title)
  print('\033[1;33m结果如下:\033[0m')
  print('-'.join(fields_list))
  for data in fields_data:
   print('-'.join(data))

总结

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