Primary keys Dbms

Question

Is it possible for table to have more than one primary key?

If no then why?

Answer 1

You cannot declare two primary keys in one table.
However, you can declare one primary key with multiple columns. This is perfectly fine. There is no requirement that a primary key (or any key) have only one column.

And if you want to know more then see the link below ..

https://www.quora.com/What-is-the-use-of-two-primary-keys-for-one-table-in-SQL

Hope this link will help you to understand the concept of primary key.

Answer 2

No it is not possible for a table to have more than one primary key . however many columns can be part of primary key which is called composite primary key .

why : it is defined as such by dbms and primary means main key so one main is fine why to declare many main keys

Comments

Hypotheticallly if we have more than one primary key, Will it have any effect on the rowids or Indexing or anywhere else?

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You never have two primary key in one table. There can be more than one candidate key in a table.
Usually to avoid having more than one candidate key in one table, you split the table and form a new one with the chosen primary key and the other candidate key(s), this allows the database to recognize any tuple from any of the splited table using one common primary key instead of relying on different keys.