Databases
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    1. COyour advice is contradictory isn't it? By suggesting that you need a "unique index" I understand you to mean that the composite key constraint should be enforced in that way. Therefore that it is still a de-facto composite key. There's nothing wrong with composite keys - they are a good thing. But in my opinion they are better if created explicitly by unique constraints (SQL UNIQUE or PRIMARY KEY constraints for example) rather than implicitly through indexes. That's assuming the DBMS in question supports unique constraints.
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      1. USsqlvogel
    2. COA unique index is not a composite key. It is not used to relate to other tables and thus is not a KEY at all. The reason why you don't want composite keys is that in relating to other tables you need to have the smallest key possible for performance. You also need something whose values will never change and that is extremly rare with composite keys. I would never consider using a database that didn't allow unique indexes, that would be just a toy not a real database.
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    3. COA key is not just something that is "used to relate to other tables". A candidate key is a set of column attributes that is required to be unique and is irreducibly so. A composite key is any candidate key with more than one attribute. Composite keys are therefore essential for effective database design. Whether any such key is referenced in another table is a different question. Also, it's quite possible for a composite key to be smaller than a single attribute key. Size is certainly a factor but it's not the only one and is rarely the most important.
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Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

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