摘要:
public class Sum { public static int count(int n) { if (n > 1) { return count(n - 1) + n; } else { return n; } } public static void main(String[] args 阅读全文
摘要:
select count(*) from extend_mobile select * from extend_mobile em where em.city='北京'; select * from extend_mobile em where em.provice='江苏'; -- 组合查询 se 阅读全文