问题：
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：
① 数据库的题，是一道两表联合查找的问题，我们需要用到Join操作，最直接的方法就是用Left Join来做，根据PersonId这项来把两个表联合起来。1596ms。
SELECT Person.FirstName,Person.LastName,Address.City,Address.State
From Person LEFT JOIN Address ON Person.PersonId = Address.PersonId;② 在使用Left Join时，我们也可以使用关键Using来声明我们想用哪个列名来进行联合。966ms。
SELECT Person.FirstName,Person.LastName,Address.City,Address.State
From Person LEFT JOIN Address USING(PersonId);③ 可以加上Natural关键字，这样我们就不用声明具体的列，MySQL可以自行搜索相同的列。1520ms。
SELECT Person.FirstName,Person.LastName,Address.City,Address.State
From Person NATURAL LEFT JOIN Address;