175. Combine two Tables "Leetcode"-left JON and right JOIN, table associated query-java-sql Getting Started

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 are the primary key column for this table.

Write a SQL query for a report this provides the following information for each person in the person table, regardless if There is a address for each of those people:

FirstName, LastName, city, state


The topic is to search two related tables, from the table to go to the keyword, but remember that the special case is the select where there is no data matching will return empty, but you like to query XX's address may be a person information?
This time we use left JON and right JOIN

What do you mean, the query results on the statement you understand?

#左连接就是左边查询的如果有数据右面如果没有匹配, then the right side of the data can be empty # SELECT  from  Left Join  on Person.personid=address.personid; #右连接就是右边查询的如果有数据左面如果没有匹配, then the right data can be empty SELECTfrom right    joinon    address.personid= Person.personid;

175. Combine two Tables "Leetcode"-left JON and right JOIN, table associated query-java-sql Getting Started