Can a primary key be Alternate Key?

Question

A Primary Key can't be an Alternate Key. For a table with a single Candidate Key which has to be the Primary Key will not contain any Alternate Key. A Foreign Key can't be an Alternate Key as it is only used to reference another table. The alternate Key should be unique. 21 июл. 2021 г.

What are alternate primary keys?

What is the Alternate key? ALTERNATE KEYS is a column or group of columns in a table that uniquely identify every row in that table. A table can have multiple choices for a primary key but only one can be set as the primary key. All the keys which are not primary key are called an Alternate Key.

Can a primary key be a secondary key?

Yes, there should be no problem. Foreign keys and primary keys are orthogonal to each other, it's fine for a column or a set of columns to be both the primary key for that table (which requires them to be unique) and also to be associated with a primary key / unique constraint in another table.

Can a primary key be a surrogate key?

Surrogates in practice. In a current database, the surrogate key can be the primary key, generated by the database management system and not derived from any application data in the database. The only significance of the surrogate key is to act as the primary key.

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