[MySQL][LeetCode][Easy] 175. Combine Two Tables

心得：

題目要求找出Person表內所有人員的地址，就算是空的也無所謂，所以不用理會Address表內是否有Person表的資料，這題必須使用LEFT JOIN來關聯。

問題：

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

答案：

# Write your MySQL query statement below
SELECT      a.FirstName, a.LastName, b.City, b.State
FROM        Person AS a
LEFT JOIN   Address AS b
ON          a.PersonId = b.PersonId

參考：

1. [SQL] 一張圖片解釋 JOIN