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~
原文：http://blog.csdn.net/exceptional_derek/article/details/43342811