Detailed explanation and options for the selected question.
What is the main purpose of a PRIMARY KEY in a table?
A.
To uniquely identify each row in a table
B.
To link two tables together
C.
To ensure that a column has no NULL values
D.
To enforce data integrity across multiple tables
Explanation:
The PRIMARY KEY uniquely identifies each row in a table. While it enforces uniqueness, it does not directly link tables or prevent NULLs without other constraints.