力扣leetcod 175:组合两个表

175:组合两个表

题：

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

编写一个 SQL 查询，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

来源：力扣（LeetCode）
链接：https://leetcode-cn.com/problems/combine-two-tables
著作权归领扣网络所有。商业转载请联系官方授权，非商业转载请注明出处。

答案 一 ：

1 select  p.FirstName as FirstName,p.LastName as LastName,a.City as City,a.State as State
2 from Person as p left join Address as a ON p.PersonId=a.PersonId;

耗时较久

答案二：

1 select  FirstName ,LastName, City,State
2 from Person
3 left join Address
4 ON Person.PersonId=Address.PersonId;

耗时稍微减少

原文地址：https://www.cnblogs.com/hukuanhu/p/12116641.html