LeetCode 175. Combine Two Tables

题目

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

题目大意 : 编写一个SQL查询，对于Person表中的每一个人，取出FirstName, LastName, City, State属性，无论其地址信息是否存在。

解题思路

• LEFT [OUT] JOIN
  表Person 与表 Address 作左外连接查询

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

LEFT JOIN 官方文档

LEFT JOIN and RIGHT JOIN