SQL/LEETCODE
[175_EASY] Combine Two Tables
소금깨
2022. 9. 23. 16:28
Table: Person
+-------------+---------+
| Column Name | Type |
+-------------+---------+
| personId | int |
| lastName | varchar |
| firstName | varchar |
+-------------+---------+
personId is the primary key column for this table.
This table contains information about the ID of some persons and their first and last names.
Table: Address
+-------------+---------+
| Column Name | Type |
+-------------+---------+
| addressId | int |
| personId | int |
| city | varchar |
| state | varchar |
+-------------+---------+
addressId is the primary key column for this table.
Each row of this table contains information about the city and state of one person with ID = PersonId.
Write an SQL query to report the first name, last name, city, and state of each person in the Person table. If the address of a personId is not present in the Address table, report null instead.
Return the result table in any order.
The query result format is in the following example.
Example 1:
Input:
Person table:
+----------+----------+-----------+
| personId | lastName | firstName |
+----------+----------+-----------+
| 1 | Wang | Allen |
| 2 | Alice | Bob |
+----------+----------+-----------+
Address table:
+-----------+----------+---------------+------------+
| addressId | personId | city | state |
+-----------+----------+---------------+------------+
| 1 | 2 | New York City | New York |
| 2 | 3 | Leetcode | California |
+-----------+----------+---------------+------------+
Output:
+-----------+----------+---------------+----------+
| firstName | lastName | city | state |
+-----------+----------+---------------+----------+
| Allen | Wang | Null | Null |
| Bob | Alice | New York City | New York |
+-----------+----------+---------------+----------+
Explanation:
There is no address in the address table for the personId = 1 so we return null in their city and state.
addressId = 1 contains information about the address of personId = 2.
문제 조건
Person 테이블에 있는 각 사람의 firstname, lastname, city, state를 출력하시오. personId가 Address 테이블에 없는 경우 city,state는 null값을 출력합니다.
문제 풀이
select firstName,
lastName,
city,
state
from person p
left join address a on p.personId = a.personId