Oracle/SQL-「無関係な」無関係なテーブルからのカウントの組み合わせ

これを試してください：

SELECT (SELECT COUNT(*) AS good 
        FROM   table_good 
        WHERE  widget = 'Widget A' 
               AND good = 'Y') AS good, 
       (SELECT COUNT(*) AS bad 
        FROM   table_bad 
        WHERE  widget = 'Widget A' 
               AND bad = 'Y')  AS bad 
FROM   dual