How many columns can a primary key have?

Question

In both these examples, primary key contains only one column. In the case of Books table, it is the BookId column and in the case of Authors , it is AuthorId .

Can a primary key have multiple columns?

A table can have only ONE primary key; and in the table, this primary key can consist of single or multiple columns (fields).

Is primary key only one column?

You can have only one primary key in a table, but it can consist of multiple columns. This doesn't mean that each column is a primary key, but that the combination of all these columns' values are unique.

What is the limit of primary key?

SQL Server Database Engine objectMaximum values for SQL Server (64-bit)Bytes per primary key900Bytes per row8,060Bytes per row in memory-optimized tables8,060Bytes in source text of a stored procedureLesser of batch size or 250 MB

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.

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