To answer this question, we need to understand the differences between VARCHAR, VARCHAR2, and STRING data types.
Option A) Both are the same - This option is incorrect because VARCHAR and VARCHAR2 are not the same. They have slight differences in their behavior and storage capacity.
Option B) Both are different - This option is partially correct. VARCHAR and VARCHAR2 are indeed different data types, but they have similar functionalities.
Option C) None of these - This option is incorrect because there are differences between VARCHAR and VARCHAR2.
Option D) The subtypes VARCHAR and STRING are equivalent to VARCHAR2 - This option is correct. In Oracle databases, the subtypes VARCHAR and STRING are equivalent to VARCHAR2. Both VARCHAR and STRING can be used interchangeably with VARCHAR2 without any differences in functionality.
The correct answer is D) The subtypes VARCHAR and STRING are equivalent to VARCHAR2.