user: Question: What is the smallest round for the Welterweight class with a Preliminary card?
Columns: ['Card', 'Weight Class', 'Round', 'Time', 'Method']
Types: ['text', 'text', 'real', 'text', 'text']
Sample row: ['Preliminary', 'Welterweight', 3.0, '5:00', 'Decision (split)']
SQL:

assistant: SELECT MIN("Round") FROM "Table" WHERE "Weight Class" = 'Welterweight' AND "Card" = 'Preliminary';