Among all the players whose weight is under 130, how many of them preferred foot in attacking is left?
weight < 130; preferred foot in attacking refers to preferred_foot; preferred_foot = 'left';
SELECT COUNT(DISTINCT t1.id) FROM Player AS t1 INNER JOIN Player_Attributes AS t2 ON t1.player_api_id = t2.player_api_id WHERE t1.weight < 130 AND t2.preferred_foot = 'left'