模拟数据库查询操作

#!/usr/src/python
# -*- coding:utf-8 -*-

# 数据预处理




# 插入数据
def ins_data():
    pass

# 删除数据
def del_data():
    pass

# 数据更新
def upd_data():
    pass

# 数据查询操作
def sel_data():
    if 'where' in v_sql:
        pass
    else:
        f = open('mydb/emp', 'r', encoding='utf-8')
        data = f.read()
        print(data)
        f.close()


'''
select * from mydb.emp where a= and b= 
UPDATE mydb.emp set a= where a=xxx
DELETE from mydb.emp where a=
insert into mydb.emp values ()
'''

v_sql_str=input('sql>')
v_sql=v_sql_str.lower()
# sql初步解析，进一步的解析在具体操作函数中处理
if 'select * from mydb.emp' in v_sql:
    sel_data()
elif 'update' in v_sql:
    upd_data()
elif 'delete' in v_sql:
    del_data()
elif 'insert' in v_sql:
    del_data()
else:
    print('dbms不支持此操作')