Join返回空值

Question

我有两张桌子，

Table: Person

+-------------+---------+
| Column Name | Type    |
+-------------+---------+
| PersonId    | int     |
| FirstName   | varchar |
| LastName    | varchar |
+-------------+---------+
PersonId is the primary key column for this table.

和

Table: Address

+-------------+---------+
| Column Name | Type    |
+-------------+---------+
| AddressId   | int     |
| PersonId    | int     |
| City        | varchar |
| State       | varchar |
+-------------+---------+
AddressId is the primary key column for this table.

我想为报告编写SQL查询，该报告为Person表中的每个人提供以下信息，无论每个人都有一个地址：

FirstName, LastName, City, State

我做了什么？

# Write your MySQL query statement below
SELECT Person.FirstName, Person.LastName, Address.City, Address.State
FROM Person
INNER JOIN Address ON Person.PersonId=Address.PersonId;

由于某种原因，join返回空数据。请给出提示而不是解决方案。

Answer 1

考虑到“无论是否有地址”短语，您正在请求LEFT JOIN。

您要求提示，而不是解决方案，因此我只留下指向a Wikipedia article on SQL Joins的链接，指向正确的方向。