er.txt

来自「ssd7考试exam2,绝对有用~欢迎下载」· 文本 代码 · 共 35 行

/*
*@author:wangzhesi
*053597
*/
*****Strong Entities*****
Branches:
    Branches_id(PK)
    Name
    Assets

Customers:
    Customers_id(PK)
    Name
    Telephone
    Address

Accounts:
    Accounts_id(PK)
    Balance

*****Weak Entities*****
Transactions:
    Transactions_id(PK)
    Operation
    Date
   
*************Relationships***************
1.has:<Branches,Accounts>,1:n,total/total
2.have:<Customers,Accounts>,1:n,total/total
3.operate:<Accounts,Transactions>,1:n,total/partial

*************Assumption*************** 
1.One customer has at least one account, one account only belongs to one customer.
2.One branch can have many accounts, an account only belongs to one and only one branch.
3.One account can has one or more transactions, a transaction has to be operated by one account.