To answer this question, let's go through each option to understand why it is correct or incorrect:
Option A) Primary key access - This option involves accessing a table using the primary key. While primary key access can be efficient for retrieving a single row, it is not always the fastest method as it depends on the table's structure and data distribution.
Option B) Access via unique index - This option involves accessing a table using a unique index. Accessing a table via a unique index can be efficient for retrieving a single row. However, it may not always be the fastest method compared to other options.
Option C) Table access by ROWID - This option involves accessing a table directly using the ROWID. The ROWID is a unique identifier for each row in a table and allows for direct access to the desired row. This method is typically the fastest way to retrieve a single row as it bypasses index lookups.
Option D) Full table scan - This option involves scanning the entire table to find the desired row. This method is generally slower compared to other options, especially when retrieving a single row.
The correct answer is C) Table access by ROWID. This option is correct because it allows for direct access to the desired row, making it the fastest way for Oracle to retrieve a single row.