【leetcode SQL】Combine Two Tables，leetcodecombine

突然发现leetcode出sql题了，找了道最简单的，找找自信。。

题目如下：

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

解决方案如下：

# Write your MySQL query statement below
select FirstName, LastName, City, State
from Person a left join Address b on  a.PersonId=b.personId

因为题目要求查询出每个人的信息，无论这个人是否登记了住址信息，所以需要用左连接~