LeetCode: 175. Combine Two Tables
上周公司安排外出培训，博客停更了一周。
题目描述
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
解题思路
左外连接(Left Outer Join)：以左表为主表的连接。接收左表的所有行，并用这些行与右表进行匹配。
右外连接(Right Outer Join)：以右表为主表的连接。接收右表的所有行，并用这些行与右表进行匹配。
内连接(Inner Join)：内联接使用比较运算符根据每个表共有的列的值匹配两个表中的行。
本题是以 Person 表为主表的外链接。
AC 代码
select FirstName, LastName, City, State
from Person
left outer join Address
on Person.PersonId = Address.PersonId;
