mysql - 连接返回空值

Question

我有两张 table ，

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.

我想为一个报表编写一个 SQL 查询，该报表为 Person 表中的每个人提供以下信息，无论每个人是否都有地址:

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，连接返回空数据。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。

您请求的是提示，而不是解决方案，因此我将仅留下指向 a Wikipedia article on SQL Joins 的链接这应该会为您指明正确的方向。