组合两个表
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:
建表语句:
Create table Person (PersonId int, FirstName varchar(255), LastName varchar(255)) Create table Address (AddressId int, PersonId int, City varchar(255), State varchar(255)) Truncate table Person insert into Person (PersonId, LastName, FirstName) values (‘1‘, ‘Wang‘, ‘Allen‘) Truncate table Address insert into Address (AddressId, PersonId, City, State) values (‘1‘, ‘2‘, ‘New York City‘, ‘New York‘)
解法:
select FirstName, LastName, City, State from Person left join Address on Person.PersonId = Address.PersonId
FirstName, LastName, City, State
来源:力扣(LeetCode)
链接:https://leetcode-cn.com/problems/combine-two-tables
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原文地址:https://www.cnblogs.com/q1359720840/p/11104559.html
时间: 2024-10-09 00:37:34