子分类的合计

        Groupby可以进行分类的合计，如果要进一步进行子分类的合计并在一行显示，关键问题是分类的字段如何被子查询使用。我试了一些办法，觉得这样可行，分类时，就把分类字段名字改了，这样就可以在子查询中使用而不会重复了。——说的比较绕，看例子还是比较清楚的。

SELECT BJ,
           (SELECT COUNT(*)
          FROM [1]
          WHERE (性别 = '男') AND (班级 = bj)) AS 男生,
           (SELECT COUNT(*)
          FROM [1]
          WHERE (性别 = '女') AND (班级 = bj)) AS 女生,
           (SELECT COUNT(*)
          FROM [1]
          WHERE (班级 = bj)) AS 总计
 FROM (SELECT 班级 AS BJ, *
         FROM [1]) DERIVEDTBL
 GROUP BY BJ

附，失败的尝试：

SELECT 班级,
           (SELECT COUNT(*)
          FROM [1] b
          WHERE (性别 = '男') AND (b.班级 = 班级)) AS 男生
 FROM [1]
 GROUP BY 班级
SELECT 班级,
 FROM [1]
 WHERE (班级 IN
           (SELECT DISTINCT 班级
          FROM [1]))