关于EER model(实体关系模型图)高人请教！

hongxin887 2011-08-09 05:13:53

现在初学基础数据库的EER模型图，有一小问题搞乱了我！

客户可以在银行开启账户，这里有不同的类型的账户（savings, checking, credit and loan accounts）
客户可以办理银行业务（取款和存钱）

取款业务只能在savings, checking accounts 上面办理，但是不能在credit and loan accounts 做取款的业务！
每次办理取款业务必须记录办理的方式如（银行出纳员，ATM取款机，或者电子交易）
ATM取款机有属于它自己的id 和地址

存钱的业务可以通过银行出纳员（可以存现金或者支票）或者通过电子交易方式
如果客户存的是支票，那么数据库必须记录支票的信息（unique cheque number, the bank that issued the cheque, the name on the cheque, date and amount）

因为这里我想用到弱实体的子类，可以我不知道能不能用。。怎么用？
还有我有个问题：我知道弱实体可以做为父类，可以有他的子类，
但是我想知道弱实体的子类可以跟强实体（一般的实体）建立关系吗？
我看的是英文的题目需要做一个关于银行的EER模型图，这只是其中一小段的描述
这是我自己翻译的。

原英文段落如下：
There are several types of accounts: savings, checking, credit and loan accounts. Each account has a unique number. The bank maintains a record of each account’s opening day, type, balance and also information about all transactions. For each customer associated with an account, the database should also store the user name for internet access and the chosen password (if appropriate). For each transaction (such as withdrawal or deposit), the database should store the date and time, the amount and the type of transaction. Withdrawals are available from checking and savings accounts, but not from credit cards or loans. For each withdrawal, it is necessary to store the manner in which the withdrawal was made (e.g. teller, ATM machine, or electronic transaction). Each ATM machine has a unique id and location. A deposit can be made via a teller (by cash or cheque) or electronically. If a customer has deposited a cheque, the database should store information about the cheque (unique cheque number, the bank that issued the cheque, the name on the cheque, date and amount).

希望有人对EER模型比较在行的给我讲解一下，我有点搞乱了。。。

还有我有个问题：我知道弱实体可以做为父类，可以有他的子类，
但是我想知道弱实体的子类可以跟强实体（一般的实体）建立关系吗？

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