The correct answer is: the number of matching rows deleted from the table and the number of new/replacing rows inserted into the table

When you use a REPLACE query, it's like a "swap" operation. It removes the matching rows from the table and inserts new rows (which can be updated or entirely new ones) in their place. So, the number of rows affected shows both the removal and insertion counts.

Here's a breakdown:

• Matching rows removed (deleted): The old data that's replaced
• New/Replacing rows inserted: The new data that's added

So, the rows affected count gives you the total of both these actions!