https://leetcode.com/problems/combine-two-tables/ Combine Two Tables Table: Person +-------------+---------+ | Column Name | Type | +-------------+---------+ | PersonId | int | | FirstName | varchar | | LastName | varchar | +-------------+---------+…

一.题目 175. Combine Two Tables 二.分析 连接查询的时候要考虑where和on的区别 where : 查询时,连接的时候是必须严格满足条件的,满足了才会加入到临时表中. on : 查询时,考虑要满足这个条件,如果不满足则不会添加连接的表中的数据. 三.AC代码 SELECT FirstName, LastName, City, State FROM Person p LEFT JOIN Address a ON p.PersonID = a.PersonID;…

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

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…

题目标签: 题目给了我们两个table,让我们合并,根据Person为主. 因为题目说了 提供person 信息,不管这个人有没有地址.所以这里用Left Join. Java Solution: Runtime:  244 ms, faster than 40 % 完成日期:05/22/2019 关键点:Left Join # Write your MySQL query statement below Select FirstName, LastName, City, State From…

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

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

因为对数据库的内容早都忘得差不多了,所以我的第一感觉是: select Person.FirstName, Person.LastName, Address.City from Person, Address where Person.PersonId=Address.PersonId 结果出错了: 因为至少这个人是存在的,只是没有她的地址,你不至于搜不到吧, 但是我这种写法是引用两个表,从两个表中获取数据,就是找两者相同的情况下的结果. 使用join 可以连接两个表: join: 如果表中有一…

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…

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,…

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 …

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

leetcode竟然有sql的题了..两道简单的应该会做 这个题主要就是一个left join... # Write your MySQL query statement below SELECT Person.FirstName, Person.LastName, Address.City, Address.State FROM Person LEFT JOIN Address ON Person.PersonId = Address.PersonId;…

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

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

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…

public class Solution { public List<List<Integer>> combinationSum3(int k, int n) { return combination(k, n, 1); } public List<List<Integer>> combination(int k, int target, int start) { List<List<Integer>> list = new Arr…

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

给定两个表,一个是人,一个是地址,要求查询所有人,可以没有地址. select a.FirstName, a.LastName, b.City, b.State from Person as a left join Address as b Using(PersonId); 详细可参考:https://www.cnblogs.com/grandyang/p/5348900.html…

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

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

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

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).…

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…

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

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…

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…