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分析

难度 易

来源

https://leetcode.com/problems/combine-two-tables/

SQL LEFT JOIN 关键字

LEFT JOIN 关键字会从左表 (table_name1) 那里返回所有的行,即使在右表 (table_name2) 中没有匹配的行。

LEFT JOIN 关键字语法

SELECT column_name(s)

FROM table_name1

LEFT JOIN table_name2

ON table_name1.column_name=table_name2.column_name

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
解答
Runtime: 184 ms, faster than 99.52% of MySQL online submissions for Combine Two Tables.
1 # Write your MySQL query statement below
2 
3 select Person.FirstName, Person.LastName,Address.City,Address.State from Person left join Address on Person.PersonId=Address.PersonId order by Person.FirstName;
posted on 2018-11-16 15:04  flowingfog  阅读(64)  评论(0编辑  收藏