如何对受第三方实体约束的 1:N 关系进行建模？
我的困境：我正在对一个会计数据库进行建模，其中客户与帐户实体的关系是一对多（1：N），但客户与办公室位置的关系是唯一的（一对一，1：1） 。我尝试找出三元关系，并将其解析为通过二元关系附加到其他三个的弱实体。我最终得到这样的结果：
OFFICE_LOC ---SERVES(M:N)=== CLIENT
OFFICE_LOC ---ANCHORS(1:N)=== ACCOUNT (WE)
CLIENT ===OWNS(1:N)= == 帐户（我们）
我很难弄清楚如何对客户在每个 office_loc 只能拥有一个帐户的条件进行建模，尽管一般来说他们可以拥有多个帐户。
My predicament: I am Chen-modelling an accounting database in which the client to account entity relationship is one-to-many (1:N), but the client to office_location relationship is unique (one-to-one, 1:1). I've tried figuring a ternary relationship and also resolving it into a weak entity attached to the other three through binary relationships. I end up with something like this:
OFFICE_LOC ---SERVES(M:N)=== CLIENT
OFFICE_LOC ---ANCHORS(1:N)=== ACCOUNT (WE)
CLIENT ===OWNS(1:N)=== ACCOUNT (WE)
I am having a tough time figuring out how to model the condition that a client can have only one account per office_loc even though they can have many accounts, generally speaking.
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我不知道您是否具体询问如何在 Chen 建模中对某些内容进行建模（我对此一无所知），或者您是否询问如何对这种关系进行数据建模。如果前者忽略这个答案，如果后者...
Client <---Client_2_Account--->帐户
除了客户和帐户的 fkey 字段之外，Client_2_Account 多对多表还将具有 Office_Location fkey 字段。对 client/office_location 的复合键和 account 的唯一键设置唯一约束。这样，一个客户在一个办公地点只能拥有一个帐户记录，并且每个帐户记录只能由一个客户拥有。
I don't know if your asking specifically how to model something in Chen modelling (which I know NOTHING about) or if you're asking how to data model this relationship. If the former ignore this answer, if the latter...
Client <---Client_2_Account---> Account
The Client_2_Account many-to-many table will have an Office_Location fkey field in addition to the fkey fields for client and account. Put a unique constraint on the compound key of client/office_location and a unique key on account. Then a client can have only one account record for an office location and each account record can be owned by only one client.