Leetcode 175. Combine Two Tables (Database)
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
本题的思路很简单，由于FirstName, LastName, City, State 来自两个不同的 table， 所以要用join。由于要求必须显示人名，即使没有地址相关信息，说明要用LEFT JOIN。经测试LEFT JOIN和LEFT OUTER JOIN效果一样。
1 # Write your MySQL query statement below 2 SELECT FirstName, LastName, City, State FROM Person 3 LEFT JOIN Address ON Person.PersonId = Address.PersonId
