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算法刷题笔记Java

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题解 | #列出供应商及其可供产品的数量#

select v.vend_id, count(p.prod_id) as prod_id from Vendors v left join Products p on v.vend_id = p.vend_id group by v.vend_id order by v.vend_id; 使用左外...

2024-03-26

0 198

题解 | #纠错4#

SELECT cust_name, cust_contact, cust_email FROM Customers Order BY cust_name; 直接使用一个select

2024-03-26

0 171

题解 | #组合 Products 表中的产品名称#

select prod_name from Products union all select cust_name as prod_name from Customers order by prod_name; 使用union all拼接两个查询结果

2024-03-26

0 160

题解 | #没有重复项数字的全排列#

import java.util.*; public class Solution { /** * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可 * * * @param num int整型一维数组 * @re...

2024-03-26

0 169

题解 | #将两个 SELECT 语句结合起来（二）#

select prod_id, quantity from OrderItems where quantity = 100 or prod_id like 'BNBG%' order by prod_id; 只使用一个select，但是是多条件，使用or连接

2024-03-22

0 142

题解 | #将两个 SELECT 语句结合起来（一）#

select prod_id, quantity from OrderItems where quantity = 100 union all select prod_id, quantity from OrderItems where prod_id like 'BNBG%' order by p...

2024-03-22

0 157

题解 | #返回产品名称和与之相关的订单号#

select p.prod_name, o.order_num from Products p left join OrderItems o on p.prod_id = o.prod_id order by p.prod_name; MySQL中的outer join分为left join、ri...

2024-03-21

0 174

题解 | #检索每个顾客的名称和所有的订单号（二）#

select c.cust_name, o.order_num from Customers c left join Orders o on c.cust_id = o.cust_id order by c.cust_name; 使用left join，保留左表所有数据，如果右表没有对应的数据则以N...

2024-03-21

0 139

题解 | #二叉树的后序遍历#

import java.util.*; /* * public class TreeNode { * int val = 0; * TreeNode left = null; * TreeNode right = null; * public TreeNode(int v...

2024-03-21

0 149

题解 | #二叉树的中序遍历#

import java.util.*; /* * public class TreeNode { * int val = 0; * TreeNode left = null; * TreeNode right = null; * public TreeNode(int v...

2024-03-21

0 183