LeetCode每日一题：Combine Two Tables

问题描述

Table: Person

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

Table: Address

+-------------+---------+
| Column Name | Type    |
+-------------+---------+
| AddressId   | int     |
| PersonId    | int     |
| City        | varchar |
| State       | varchar |
+-------------+---------+
AddressId is the primary key column for this table.

Write a SQL query for a report that provides the following information for each person in the Person table, regardless if there is an address for each of those people:

FirstName, LastName, City, State

问题分析

合并两个表格，且使用左连接。

LEFT JOIN.png

代码实现

SELECT Person.FirstName,Person.LastName,Address.City,Address.State
FROM Person LEFT OUTER JOIN Address
ON Person.PersonId=Address.PersonId;