Combine Two Tables # Write your MySQL query statement below Select p.FirstName, p.LastName, a.City, a.State from Person p left join Address a on p.PersonId = a.PersonId Consecutive Numbers # Write your MySQL query statement below select distinct num…

Coding on LeetCode Online Judge leetcode(leetcode website) Problems algorithms 13. Roman to Integer 12. Integer to Roman 11. Container With Most Water 10. Regular Expression Matching Recursion 递归 9. Palindrome Number 8. String to Integer (atoi) 7. Re…

LeetCode有10道SQL的题目,最近学习SQL语言,顺便刷题强化一下, 说实话刷完SQL学习指南这本书,不是很难,上面的例子 跟语法规则我都能理解透, 实际中来做一些比较难的业务逻辑题,却一下子很难想起如何利用SQL来描述 还是要多刷题开阔自己的思路,把学到手的语法加以练习 应用到实际中去 197. Rising Temperature Given a Weather table, write a SQL query to find all dates' Ids with higher t…

题目链接:https://leetcode.com/problems/nth-highest-salary/description/ 题意:查询出表中工资第N高的值 思路: 1.先按照工资从高到低排序(注意去重) select distinct Salary from Employee order by Salary desc 2.使用rownum给查询出的数据标注行号 select rownum ro, s.Salary from (select distinct Salary from Em…

Write a SQL query to delete all duplicate email entries in a table named Person, keeping only unique emails based on its smallest Id. +----+------------------+ | Id | Email | +----+------------------+ | 1 | john@example.com | | 2 | bob@example.com |…

Write a SQL query to rank scores. If there is a tie between two scores, both should have the same ranking. Note that after a tie, the next ranking number should be the next consecutive integer value. In other words, there should be no "holes" be…

Consecutive Numbers Write a SQL query to find all numbers that appear at least three times consecutively. +----+-----+ | Id | Num | +----+-----+ | 1 | 1 | | 2 | 1 | | 3 | 1 | | 4 | 2 | | 5 | 1 | | 6 | 2 | | 7 | 2 | +----+-----+ For example, given the…

175. Combine Two Tables 使用外连接即可. # Write your MySQL query statement below select FirstName, LastName, City, State from Person left outer join Address on Person.PersonId = Address.PersonId; # Write your MySQL query statement below select p.FirstName,…

Combine Two Tables Table: Person +-------------+---------+ | Column Name | Type | +-------------+---------+ | PersonId | int | | FirstName | varchar | | LastName | varchar | +-------------+---------+ PersonId is the primary key column for this table.…

175 Combine Two Tables 题目:左连接Person表和Address表. select FirstName,LastName,City,State from Person p left join Address a on p.PersonId=a.PersonId; 7个case耗时1001ms(注意耗时多次提交会不同,一般相差不大,偶尔也有相差大的)   --2015/1/11 176 Second Highest Salary 题目:写一条sql语句查询Employee …

X city built a new stadium, each day many people visit it and the stats are saved as these columns: id, date, people Please write a query to display the records which have 3 or more consecutive rows and the amount of people more than 100(inclusive).…

Note: For the coding companion problem, please see: Encode and Decode TinyURL. How would you design a URL shortening service that is similar to TinyURL? Background:TinyURL is a URL shortening service where you enter a URL such as https://leetcode.com…

原题链接在这里:https://leetcode.com/problems/design-tinyurl/description/ 题目: How would you design a URL shortening service that is similar to TinyURL? Background:TinyURL is a URL shortening service where you enter a URL such as https://leetcode.com/problems…

https://leetcode.com/problemset/database/ ACM退役,刚好要学sql,一定要刷题才行,leetcode吧. 这一题,说了两个表,一个左一个右吧,左边的personId是唯一的,但是右边的PersonId是不唯一的,所以不去重. 然后,总结下各种join的用法. 1.inner join,On XXX,需要左边有,右边也有,就输出该行. 2.outer join / 有些书叫 full join,左边有,右边没,也输出,右边没的就用NULL代替.同理右边有…

leetcode 主要是一个针对北美的coder人群找工作的代码练习网站,我在2015年初次接触这个网站的时候,总共只有200多道题目,是一个类似acm 的a题网站.这些年变化越来越大,主要是因为找工作当然是多样化的考核过程,leetcode 也逐渐与时俱进,推出了下面几个类别的联系,今天我们随便挑几个练习一下: 175. Combine Two Tables -SQL Table: Person Column Name Type PersonId int FirstName varchar L…

Note: For the coding companion problem, please see: Encode and Decode TinyURL. How would you design a URL shortening service that is similar to TinyURL? Background:TinyURL is a URL shortening service where you enter a URL such as https://leetcode.com…

LeetCode 算法面试题汇总 算法面试题 https://leetcode-cn.com/problemset/algorithms/ https://leetcode-cn.com/problemset/database/ https://leetcode-cn.com/problemset/shell/ https://leetcode-cn.com/problemset/concurrency/ problemset 程序员面试经典(第 6 版) https://leetcode-cn…

力扣:https://leetcode-cn.com/ 力扣网数据库练习:https://leetcode-cn.com/problemset/database/ 文章目录 175. 组合两个表 题解: 1. LeetCode官方题解 2. 执行时间最快的mysql语句 笔记:on与where的区别 176. 第二高的薪水 题解: 1. LeetCode官方题解 2. 执行时间最快的mysql语句 笔记:关于解题思路与limit.isnull等 177. 第N高的薪水 题解: 1. LeetCo…

简介 在数据库的迁移和升级场景中,我们经常会遇到一个问题:在做压力测试时,如何模拟真实的业务压力,解决这个问题的方法有很多,比如:应用方开发模拟程序或者使用压力测试工具模拟,如load runner,但是,如果要说哪种方法能最大限度地模拟真实业务压力,我认为还是Oracle的Database Replay(数据库重放)功能,Database Replay功能是Real Application Testing的一部分,它的基本原理图如下: 简单说,Database Replay可以在生产数据库上“…

# 增强学习成果 有一个研究成果,在学习中传授他人知识和讨论是最高效的做法,而看书则是最低效的做法(具体研究成果没找到地址).我写LeetCode博客主要目的是增强学习成果.当然,我也想出名,然而不知道能否出名. # 给算法的新手们提供一种思考方式的参考 提前说明,本人也不是高手. 算法这个东西有点玄乎.很多新手(包括我)初期入门的时候都学的是<算法导论>,然而我并不觉得<算法导论>是一本学习算法很好的书. 我们设计算法的流程,并不是像<算法导论>那样,好像天生就知道这…

什么是Data Redaction Data Redaction是Oracle Database 12c的高级安全选项之中的一个新功能,Oracle中国在介绍这个功能的时候,翻译为“数据编纂”,在EM12c R3的中文界面中,这个功能被翻译成“数据编写”,我认为后一个翻译更贴切. 在12c发布前,某次以“数据库安全”为题目的技术交流中,有一个客户问我们,Oracle数据库里面能不能实现这么一个功能:符合条件的用户可以看到表里面的所有数据,而另外一些人(业务权限低的用户)虽然能查询表,但是某些敏感…

概述 众所周知,在业务高峰期,某些针对Oracle数据库的操作具有很高的风险,比如修改表结构.修改实例参数等等,如果没有充分评估和了解这些操作所带来的影响,这些操作很可能会导致故障,轻则导致应用错误,重则导致数据库服务不可用. 另外,在非业务高峰期,某些看似风险不大的操作也可能会导致严重后果,比如不按管理流程修改表结构,如果这个表正好是Oracle GoldenGate复制组的一部分,修改了源端结构而没有通知OGG的相关人员,没有在目标端进行相同的操作,而DDL复制功能也没有打开的情况下,就会导…

集群概念介绍(一)) 白宁超 2015年7月16日 概述:写下本文档的初衷和动力,来源于上篇的<oracle基本操作手册>.oracle基本操作手册是作者研一假期对oracle基础知识学习的汇总.然后形成体系的总结,一则进行回顾复习,另则便于查询使用.本图文文档亦源于此.阅读Oracle RAC安装与使用教程前,笔者先对这篇文章整体构思和形成进行梳理.由于阅读者知识储备层次不同,我将从Oracle RAC安装前的准备与规划开始进行整体介绍安装部署Oracle RAC.始于唐博士指导,对数据库集…

终于将LeetCode的免费题刷完了,真是漫长的第一遍啊,估计很多题都忘的差不多了,这次开个题目汇总贴,并附上每道题目的解题连接,方便之后查阅吧~ 477 Total Hamming Distance 44.10% Meidum 475 Heaters  30.20% Easy 474 Ones and Zeroes  34.90% Meidum 473 Matchsticks to Square  31.80% Medium 472 Concatenated Words 29.20% Hard…

Find the length of the longest substring T of a given string (consists of lowercase letters only) such that every character in T appears no less than k times. Example 1: Input: s = "aaabb", k = 3 Output: 3 The longest substring is "aaa"…

题目链接:Path Sum II | LeetCode OJ Given a binary tree and a sum, find all root-to-leaf paths where each path's sum equals the given sum. For example: Given the below binary tree and sum = 22, 5 / \ 4 8 / / \ 11 13 4 / \ / \ 7 2 5 1 return [ [5,4,11,2],…

题目链接:Path Sum | LeetCode OJ Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum. For example: Given the below binary tree and sum = 22, 5 / \ 4 8 / / \ 11…

题目链接:Balanced Binary Tree | LeetCode OJ Given a binary tree, determine if it is height-balanced. For this problem, a height-balanced binary tree is defined as a binary tree in which the depth of the two subtrees of every node never differ by more tha…

题目链接:Same Tree | LeetCode OJ Given two binary trees, write a function to check if they are equal or not. Two binary trees are considered equal if they are structurally identical and the nodes have the same value. Tags: Depth-first Search 分析 很基本的一道深度优…

题目链接:Recover Binary Search Tree | LeetCode OJ Two elements of a binary search tree (BST) are swapped by mistake. Recover the tree without changing its structure. Note: A solution using O(n) space is pretty straight forward. Could you devise a constan…