Last updated on January 21st, 2025 at 11:01 pm

Here, we see the Combine Two Tables LeetCode Solution. This Leetcode problem is solved using MySQL and Pandas.

List of all LeetCode Solution

Level of Question

Easy

Combine Two Tables LeetCode Solution

1. Problem Statement

Write a solution 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.

Column Name	Type
PersonId	int
FirstName	varchar
LastName	varchar

Column Name	Type
AddressId	int
PersonId	int
City	varchar
State	varchar

The result format is in the following example.

Example 1:
Input:

personId	lastName	firstName
1	Wang	Allen
2	Alice	Bob

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.

2. Code Implementation in Different Languages

2.1 Combine Two Tables MySQL

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

2.2 Combine Two Tables Pandas

import pandas as pd

def combine_two_tables(person: pd.DataFrame, address: pd.DataFrame) -> pd.DataFrame:
    result = pd.merge(person, address, on='personId', how='left')
    result = result[['firstName', 'lastName', 'city', 'state']]
    return result