[LeetCode] Combine Two Tables 组合

中文题目

表1: Person

+-------------+---------+
| 列名 | 类型 |
+-------------+---------+
| PersonId | int |
| FirstName | varchar |
| LastName | varchar |
+-------------+---------+
PersonId 是上表主键.
表2: Address

+-------------+---------+
| 列名 | 类型 |
+-------------+---------+
| AddressId | int |
| PersonId | int |
| City | varchar |
| State | varchar |
+-------------+---------+
AddressId 是上表主键.

写一个 SQL 查询语句，满足条件：无论 person 是否有地址信息，都需要基于上述两表提供 person 的以下信息：

FirstName, LastName, City, State

英文题目

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

参考答案

方法一：

SELECT p.FirstName, p.LastName, a.City, a.State FROM Person2 p LEFT JOIN Address a USING (PersonId)

方法二：

SELECT p.FirstName, p.LastName, a.City, a.State FROM Person2 p LEFT JOIN Address a ON(p.PersonId = a.PersonId)

方法三：

SELECT p.FirstName, p.LastName, a.City, a.State FROM Person2 p,Address a WHERE p.PersonId = a.PersonId