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

 

LeetCode还出了是来到数据库的题，来那么也来做做吧，这道题是第一道，相对来说比较简单，是一道两表联合查找的问题，我们需要用到Join操作，关于一些Join操作可以看我之前的博客，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：

 

解法一：

SELECT Person.FirstName, Person.LastName, Address.City, Address.State FROM Person LEFT JOIN Address ON Person.PersonId = Address.PersonId;

 

在使用Left Join时，我们也可以使用关键Using来声明我们相用哪个列名来进行联合：

 

解法二：

SELECT Person.FirstName, Person.LastName, Address.City, Address.State FROM Person LEFT JOIN Address USING(PersonId);

 

或者我们可以加上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：

 

解法三：

SELECT Person.FirstName, Person.LastName, Address.City, Address.State FROM Person NATURAL LEFT JOIN Address;

 

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