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
Answer:
思路:因each person
and regardless address
,采用LEFT JOIN
# Write your MySQL query statement below
SELECT
FirstName,
LastName,
City,
State
FROM
person
LEFT JOIN address ON person.PersonId = address.PersonId
附SQL各种JOIN
关系图:
还有下面这个图: