175. Combine Two Tables

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

本题主要考察sql中left join、right join、innner join的使用和其中的区别。

select Person.FirstName, Person.LastName, Address.City, Address.State 
from Person
left join Address
on Person.PersonId=Address.PersonId;

SQL 连接：

1. INNER JOIN：如果表中有至少一个匹配，则返回行；

2. LEFT JOIN：即使右表中没有匹配，也从左表返回所有的行；

3. RIGHT JOIN：即使左表中没有匹配，也从右表返回所有的行