多个colums入门密钥与一个具有唯一约束的入门密钥

Question

I have large table on my database (50 columns and might get to 100,000,000 rows). Right now my primary key is 8 columns.

It is better to make 1 primary key (automatic number) and add columns unique constrains?

Answer 1

I would vote to close your question because it is too broad. However, you seem to be new to the site, and just closing the question wouldn't help.

The structure of a database should be driven by how the data is going to be used. You have not specified what you are doing with the data, so it is impossible to say that one way is "better" or "worse". One can make a judgement that the structure is normalized or denormalized, for instance. But each of those methodologies is appropriate in different circumstances.

That said, I am heavily biased to having an auto incrementing ("identity") primary key in all tables. This is beneficial in many circumstances. Here are three reasons:

• For knowing the insertion order of rows (to a close approximation).
• For creating foreign key relationships.
• To ensure that you can uniquely identify each row for updates and deletes.

However, such a column occupies more storage. And, a single primary key index is more efficient (space-wise) than having multiple indexes.

This isn't a direct answer to your question, because the answer is too vague. It does at least give you some parameters for thinking about the issues.

Answer 2

Usually when you don't know any better, it's best to follow the standard guidelines in DB design. Because they work for a clear majority of the cases, and there's less chance in going wrong with them.

In this case, it means that you would very likely benefit from using an auto-incrementing ID column as a clustered primary key index. As well as adding foreign keys and nonclustered indexes to all referencing columns, in case you haven't already.

Finally, you might even look at adding a few custom (even multicolumn) indexes specifically designed for your slowest queries... basically, if you have a few problem queries, you want to index the columns in their WHERE clauses.

In addition to all this, you should of course look to see that the table and DB in general is normalized. To learn about normalization, it's best for you to google for it. It's not a complex or difficult concept, but there are a thousand tutorials far better suited for explaining the concept than us here.

By doing this you will very likely be moving in the correct direction. And if it doesn't work, then that's so much more information people here can use to determine the best alternative.