Combine Two Tables LeetCode Solution

Problem – Combine Two Tables LeetCode Solution

SQL Schema

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.

Combine Two Tables LeetCode Solution in MySQL

SELECT FirstName, LastName, City, State
FROM Person LEFT JOIN Address USING (PersonId)

Combine Two Tables LeetCode Solution in MS SQL Server

select p.FirstName, p.LastName, a.City, a.State 
from Person as P left join Address a on a.PersonId = p.PersonId

Combine Two Tables LeetCode Solution in Oracle

SELECT firstName, lastName, city, state FROM Person p LEFT JOIN Address a ON p.personId = a.personId;

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