Does every SQL table need a primary key?

Question

In the Week 8 shorts, Mr. Lloyd is talking about a set of Seinfeld related tables. The first has a primary key but the second does not. I was under the impression that every table needed to include keys, am I wrong about that?

Thanks

Answer 1

Yes, you are wrong. But it's not an unreasonable assumption.

A Primary Key is literally the primary restriction on data of a table. It puts restrictions on duplicate data on the table.

But there's nothing that says that there needs to be any kind of restrictions on duplicate data. You can create a table with no keys whatsoever, and allow unlimited duplicate data. Even then, it is still allowable to put an index on that table.

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