#select email from (select email, count(*) as sum from Person group by email) tmp where tmp.sum >= 2;#以邮件字段进行分组,然后用having进行过滤select Emailfrom Persongr Read More
1、树结构类 public class TreeNode<T> { T val; TreeNode<T> parent; TreeNode<T> right; TreeNode<T> left; public TreeNode(){ } public TreeNode(T val){ this.va Read More
public class Tree { public static void main(String[] args) { Tree root = new Tree(50); Tree.insert(root, 30); Tree.insert(root, 60); Tree.insert(root, Read More