Question Details

Detailed explanation and options for the selected question.

Which of the following is a primary key in a database?

A. A unique identifier for each record in a table
B. A column that can have duplicate values
C. A column that allows NULL values
D. A column used only for indexing

Explanation:

The primary key uniquely identifies each record in a table and cannot have NULL or duplicate values. Option B allows duplicates, Option C allows NULLs, and Option D is used for indexing but may not enforce uniqueness.