Can you have several primary keys?

Question

The PRIMARY KEY constraint uniquely identifies each record in a table. Primary keys must contain UNIQUE values, and cannot contain NULL values. A table can have only ONE primary key; and in the table, this primary key can consist of single or multiple columns (fields).

Can you have 3 primary keys?

A table can only ever have a one primary key. It is not possible to create a table with two different primary keys. You can create a table with two different unique indexes (which are much like a primary key) but only one primary key can exist.

Can an entity have 2 primary keys?

Yes, you can have Composite primary keys, that is, having two fields as a primary key.

How many primary keys can have in a?

The PRIMARY KEY constraint specifies that the constrained columns' values must uniquely identify each row. A table can only have one primary key, but it can have multiple unique constraints.

Can a column have multiple primary keys?

A table can have only one PRIMARY KEY either on one column or multiple columns. When multiple columns are defined as PRIMARY KEY, then, it is called COMPOSITE KEY.

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