task: #602

Author: Ivanbyone

README.md

@@ -57,6 +57,7 @@ Have a good contributing!
 2. [Medium](./leetcode/medium/)
     - [176. Second Highest Salary](./leetcode/medium/176.%20Second%20Highest%20Salary.sql)
     - [184. Department Highest Salary](./leetcode/medium/184.%20Department%20Highest%20Salary.sql)
+    - [602. Friend Requests II: Who Has the Most Friends](./leetcode/medium/602.%20Friend%20Requests%20II:%20Who%20Has%20the%20Most%20Friends.sql)
     - [1045. Customers Who Bought All Products](./leetcode/medium/1045.%20Customers%20Who%20Bought%20All%20Products.sql)
     - [1070. Product Sales Analysis III](./leetcode/medium/1070.%20Product%20Sales%20Analysis%203.sql)
     - [1158. Market Analysis 1](./leetcode/medium/1158.%20Market%20Analysis%201.sql)

leetcode/medium/602. Friend Requests II: Who Has the Most Friends.sql

@@ -0,0 +1,37 @@
+/*
+Question 602. Friend Requests II: Who Has the Most Friends
+Link: https://leetcode.com/problems/friend-requests-ii-who-has-the-most-friends/description/
+
+Table: RequestAccepted
+
++----------------+---------+
+| Column Name    | Type    |
++----------------+---------+
+| requester_id   | int     |
+| accepter_id    | int     |
+| accept_date    | date    |
++----------------+---------+
+(requester_id, accepter_id) is the primary key (combination of columns with unique values) for this table.
+This table contains the ID of the user who sent the request, the ID of the user who received the request, and the date when the request was accepted.
+ 
+
+Write a solution to find the people who have the most friends and the most friends number.
+
+The test cases are generated so that only one person has the most friends.
+*/
+
+WITH id_table AS (
+    SELECT requester_id AS id
+    FROM RequestAccepted
+    UNION ALL 
+    SELECT accepter_id AS id
+    FROM RequestAccepted
+)
+
+SELECT 
+    id,
+    COUNT(id) AS num
+FROM id_table
+GROUP BY id
+ORDER BY COUNT(id) DESC
+LIMIT 1