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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:
First Name , Last Name, City, State
题意:
给定两个表person和address,然后需要将此俩表合并,并且题目中说了,不考虑能不能找到每一个人是否有存在城市和州的地址信息。那么从这句话中就可以判断出,需要用到连接,而且是左连接。因为这是将两张表合并,因此,必然是一个连接问题;此外,对于不考虑人的地址信息,那么在合并两表的时候,可以用左连接将右表中不存在的右表数据置为null。
代码如下:
select p.FirstName,p.LastName,a.City,a.State from Person as p left join Address as a on p.PersonId = a.PersonId;
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