The TRANS_SUMMARY table contains product-wise transaction details that get updated with every transaction in the system. Each row has cumulative transaction details of a single product and every…

MERGE (also called UPSERT) evaluates each source row against the target table - when a matching product code exists it performs an UPDATE, and when no match is found it performs an INSERT. This exactly satisfies the requirement that existing products are updated and new products are added each quarter. Using MERGE also avoids primary key constraint violations that a plain INSERT would cause for already-existing rows.

SQL*Loader is designed to load data from external flat files into Oracle tables, not to transfer data between two tables that already exist within the same database.

A correlated UPDATE can only modify existing rows in the target table; it cannot insert rows for new products that do not yet exist in TRANS_SUMMARY_DUP.

A plain INSERT would attempt to insert all rows including those with product codes already present in TRANS_SUMMARY_DUP, causing primary key constraint violations for existing products.