SQL - 我是否应该使用连接表？
我正在创建一个新的 SQL Server 2008 数据库。我有两个相关的两个表。
第一个表如下所示：
BRANDS // table name
BrandID // pk
BrandName // varchar
第二个表如下所示：
MODELS // table name
ModelID // pk
ModelDescription // varchar
每个品牌将至少有一个型号，并且每个型号仅属于一个品牌。
问题是，我应该创建一个像这样的连接表
BRANDS_MODELS // table name
RecordID // pk
BrandID
ModelID
还是应该修改 MODELS 表以包含像这样的 BrandID
MODELS // table name
BrandID //
ModelID // pk
ModelDescription // varchar
谢谢！
I am creating a new SQL Server 2008 database. I have two two tables that are related.
The first table looks like this:
BRANDS // table name
BrandID // pk
BrandName // varchar
The second table looks like this:
MODELS // table name
ModelID // pk
ModelDescription // varchar
Every brand will have at least one model and every model will belong to only one brand.
The question is, should I create a junction table like this
BRANDS_MODELS // table name
RecordID // pk
BrandID
ModelID
Or should I modify the MODELS table to include the BrandID like this
MODELS // table name
BrandID //
ModelID // pk
ModelDescription // varchar
Thanks!
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如果一个模型只属于一个品牌，那么您可以将 FK 品牌放在模型表上（第二种方法）。第一种方法使用联结表，用于多对多关系。
If a model belongs to only one brand then you can put the FK to brand on the model table (your second approach). The first way, with the junction table, is for a many-to-many relation.
根据您到目前为止所说的，我将省略连接表并在 MODELS 表中使用普通外键。
但是，如果模型可以移动品牌，并且您需要维护当前的连接和历史记录，则连接表比仅在外键更改时保留整个 MODELS 行的历史记录具有优势。此外，如果存在其他可能与关系“实体”相关联而不是与模型实体相关联的事物，那么拥有一个联结表可能更有意义。您始终可以对联结表中的 ModelID 进行唯一约束，以确保同一型号不会链接到多个品牌。因此，尽管需要联结表来有效实现多对多关系，但它对于关系本身具有属性的一对多关系也很有用。
Based on what you've said so far, I would leave out the junction table and use an ordinary foreign key in the MODELS table.
But if a model could move brands and you needed to maintain a current junction and history, a junction table has advantages over keeping history of the entire MODELS row when just a foreign key changes. Also if other things exist which might be associated with the relationship "entity" more than the MODEL entity it might make more sense to have a junction table. You can always make a unique constraint on ModelID in the junction table to ensure that the same model is not linked to multiple brands. So although a junction table is required to effectively implement a many-to-many relationship, it can also be useful for one-to-many relationships where that relationship itself has attributes.
连接表用于多对多关系，这似乎不太适合这里。
例如，您不想启用本田思域和丰田思域的创建。这是汽车品牌/型号关系的示例，但应该适合您的品牌/型号关系。
Junction tables are used for many-to-many relationships which does not seem to be a good fit here.
For example, you would not want to enable the creation of a Honda Civic and a Toyota Civic. That's an example of car's make/model relationship but should fit your brand/model relationship.