Among the players that weigh more than 90 kg, how many of them have a position of defense?
weigh more than 90 kg refers to weight_in_kg > 90; position of defense refers to position_info = 'D' ;
SELECT COUNT(T1.ELITEID) FROM PlayerInfo AS T1 INNER JOIN weight_info AS T2 ON T1.weight = T2.weight_id WHERE T2.weight_in_kg > 90 AND T1.position_info = 'D'