175. Combine Two Tables

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本文介绍了一个SQL查询案例，通过左连接实现从Person表和Address表中获取每个人的详细信息，包括姓名、城市和州，即使某些人可能没有地址信息。

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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

两个表信息查询，使用了left join

Person表左连接 Address表查询,不能用条件查询,因为不管该人是否有地址(regardless if there is an address for each of those people)
select firstname,lastname,city,state
from person left join address on person.personid = address.personid