oracle 没有主键的表的休眠映射
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Hibernate mapping for a table with no primary key
提问by Nathan Spears
I know this question has been asked before but I have a design question as well.
我知道以前有人问过这个问题，但我也有一个设计问题。
There are two tables like so:
有两张这样的表：
Table Group_table
column pk_Group_name
column group_type
etc
Table Group_members
column fk_group_name -> foreign key to group_table
column group_member
It's easy to work with this structure but I have two questions. First, how should I map group_members in Hibernate mapping? Hibernate wants an id of some sort and I'm not sure what to tell it.
使用这种结构很容易，但我有两个问题。首先，我应该如何在 Hibernate 映射中映射 group_members？Hibernate 需要某种类型的 id，但我不知道该告诉它什么。
Second, although perhaps I should ask it first, is this bad db design? Should there be a pk on the group_members table, like a sequence or something?
其次，虽然也许我应该先问一下，这是糟糕的数据库设计吗？group_members 表上是否应该有一个 pk，例如序列或其他什么？
Also, this is an Oracle db: is there some autogenerated id I can use despite the (possibly) poor db design?
此外，这是一个 Oracle 数据库：尽管（可能）糟糕的数据库设计，我是否可以使用一些自动生成的 ID？
采纳答案by Pascal Thivent
You absolutely need an identifier in the mapping that describes how a row is unique: by PK, assigned, or composite. In your case, you could maybe use a composite-id:
您绝对需要映射中的标识符来描述行的唯一性：通过 PK、分配或组合。在您的情况下，您可以使用composite-id：
<class name="eg.Foo" table"FOOS">
<composite-id name="compId" class="eg.FooCompositeID">
<key-property name="string"/>
<key-property name="short"/>
</composite-id>
<property name="name"/>
....
</class>
Of course, this assumes the couple (fk_group_name, group_member) is unique. But this is not ideal, you should have a PK.
当然，这假设这对 (fk_group_name, group_member) 是唯一的。但这并不理想，你应该有一个PK。
Reference
参考
回答by Aaron Digulla
- Always add a PK.
- Never use a business key (like a name) as a foreign key. What happens if a user marries? Or a group renames itself? Always use a PK.
- Hibernate does handle this for you. Just add an ID column and map it as "native" (see the docs)
- 总是添加一个PK。
- 切勿使用业务键（如名称）作为外键。如果用户结婚了会怎样？或者一个组重命名自己？始终使用PK。
- Hibernate 确实为您处理了这个问题。只需添加一个 ID 列并将其映射为“本机”（请参阅文档）
