If a table has a defined clustering key and you omit the second argument in system$clustering_information, what is returned?

• A. It returns an error.
• B. It returns information for all columns.
• C. It uses the defined clustering key.
• D. It returns nothing.

Answer: (C)

Omitting the second argument makes the function default to the clustering key defined on the table. In that case, it returns clustering information for that key, letting you see how well the data is organized along your defined clustering path and assess potential benefits from reclustering. If you later specify a column or expression, the information would be for that specific target instead.