LeeCode(Database)-Combine Two Tables】的更多相关文章

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/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 +--…
Table: Person +-------------+---------+ | Column Name | Type | +-------------+---------+ | PersonId | int | | FirstName | varchar | | LastName | varchar | +-------------+---------+ PersonId is the primary key column for this table. Table: Address +--…
Suppose that a website contains two tables, the Customers table and the Orders table. Write a SQL query to find all customers who never order anything. Table: Customers. +----+-------+ | Id | Name | +----+-------+ | 1 | Joe | | 2 | Henry | | 3 | Sam…
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…
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;…
Write a SQL query to find all duplicate emails in a table named Person. +----+---------+ | Id | Email | +----+---------+ | 1 | a@b.com | | 2 | c@d.com | | 3 | a@b.com | +----+---------+ For example, your query should return the following for the abov…