Quais são os menores ativos com uma empresa de banco Piraeus, e uma receita (US$ bilhões) inferior a 3,9?
CREATE TABLE table_name_16 (assets__us INTEGER, company VARCHAR, revenues__us$_billion_ VARCHAR)
SELECT MIN(assets__us) AS $_billion_ FROM table_name_16 WHERE company = "piraeus bank" AND revenues__us$_billion_ < 3.9