Option A is the MOST efficient and recommended approach- It combines CTAS with the
'QUALIFY clause and 'ROW NUMBER()' window function to perform the transformations and deduplication in a single step. The 'QUALIFY clause filters the results based on the row number within each partition (customer_id), ensuring that only the row with the highest 'load_date' is included. Using window functions within a CTAS statement is highly optimized in Snowflake.
Option B is incorrect because 'GROUP BY with doesnt guarantee that all other columns will correspond to the record with the maximum load_date for that customer_id. Option C can unexpected results, as the subquery might return multiple maximum load dates for different customer IDs_ Option D only uses 'DISTINCT and 'ORDER BY , which does not correctly handle duplicate records and only sorts the end result Option E creates the table first, then attempts to delete duplicates, which is less efficient than doing it in a single CTAS statement.