Hackerrank

my hackerrank solution about sql - most use Mysql

Problem	Solution	Difficulty	Submission Date	note
Revising the Select Query I	solution	Easy	2025-02
Revising the Select Query II	solution	Easy	2025-02
Select All	solution	Easy	2025-02
Select By ID	solution	Easy	2025-02
Japanese Cities' Attributes	solution	Easy	2025-02
Japanese Cities' Names	solution	Easy	2025-02
Weather Observation Station 1	solution	Easy	2025-02
Weather Observation Station 3	solution	Easy	2025-02
Weather Observation Station 4	solution	Easy	2025-02
Weather Observation Station 5	solution	Easy	2025-02
Weather Observation Station 6	solution	Easy	2025-02
Weather Observation Station 7	solution	Easy	2025-02
Weather Observation Station 8	solution	Easy	2025-02
Weather Observation Station 9	solution	Easy	2025-02
Weather Observation Station 10	solution	Easy	2025-02
Weather Observation Station 11	solution	Easy	2025-02
Weather Observation Station 12	solution	Easy	2025-02
Higher Than 75 Marks	solution	Easy	2025-02
Employee Names	solution	Easy	2025-02
Employee Salaries	solution	Easy	2025-02
Type of Triangle	not solved	Easy	2025-02
The PADS	solution	Medium	2025-02
Occupations	solution	Medium	2025-02	wrong_answer, my_sql: group_concat, postgresql: string_agg, oracle: listagg
Binary Tree Nodes	solution	Medium	2025-02
New Companies	solution	Medium	2025-02
Revising Aggregations - The Count Function	solution	Easy	2025-02
Revising Aggregations - The Sum Function	solution	Easy	2025-02
Revising Aggregations - Averages	solution	Easy	2025-02
Average Population	solution	Easy	2025-02
Japan Population	solution	Easy	2025-02
Population Density Difference	solution	Easy	2025-02
The Blunder	solution	Easy	2025-02
Top Earners	solution	Easy	2025-02
Weather Observation Station 2	solution	Easy	2025-02
Weather Observation Station 13	solution	Easy	2025-02
Weather Observation Station 14	solution	Easy	2025-02
Weather Observation Station 15	solution	Easy	2025-02
Weather Observation Station 16	solution	Easy	2025-02
Weather Observation Station 17	solution	Easy	2025-02
Weather Observation Station 18	solution	Medium	2025-02
Weather Observation Station 19	solution	Medium	2025-02
Weather Observation Station 20	solution	Medium	2025-02
Population Census	solution	Easy	2025-02
African Cities	solution	Easy	2025-02
Average Population of Each Continent	solution	Easy	2025-02
The Report	solution	Medium	2025-02
Top Competitors	solution	Medium	2025-02
Ollivander's Inventory	solution	Medium	2025-02
Challenges	solution	Medium	2025-02
Contest Leaderboard	solution	Medium	2025-02
SQL Project Planning	solution	Medium	2025-02	wrong_answer, resolved
Placements	solution	Medium	2025-02
Symmetric Pairs	solution	Medium	2025-02
Interviews	solution	Hard	2025-02
15 Days of Learning SQL	not_solved	Hard

LeetCode

my letcode solution about sql - most use Postgresql

Problem	Solution	Difficulty	Submission Date	note
Recyclable and Low Fat Products	solution	Easy	2025-03
Find Customer Referee	solution	Easy	2025-03
Big Countries	solution	Easy	2025-03
Article Views I	solution	Easy	2025-03
Invalid Tweets	solution	Easy	2025-03
Replace Employee ID With The Unique Identifier	solution	Easy	2025-03
Product Sales Analysis I	solution	Easy	2025-03
Customer Who Visited but Did Not Make Any Transactions	solution	Easy	2025-03
Rising Temperature	solution	Easy	2025-03
Average Time of Process per Machine	solution	Easy	2025-03
Employee Bonus	solution	Easy	2025-03
Students and Examinations	solution	Easy	2025-03
Managers with at Least 5 Direct Reports	solution	Medium	2025-03
Confirmation Rate	solution	Medium	2025-03
Not Boring Movies	solution	Easy	2025-03
Average Selling Price	solution	Easy	2025-03
Project Employees I	solution	Easy	2025-03
Percentage of Users Attended a Contest	solution	Easy	2025-03
Queries Quality and Percentage	solution	Easy	2025-03
Monthly Transactions I	solution	Medium	2025-03
Immediate Food Delivery II	solution	Medium	2025-03
Game Play Analysis IV	solution	Medium	2025-03
Number of Unique Subjects Taught by Each Teacher	solution	Easy	2025-03
User Activity for the Past 30 Days I	solution	Easy	2025-03
Product Sales Analysis III	solution	Medium	2025-03
Classes More Than 5 Students	solution	Easy	2025-03
Find Followers Count	solution	Easy	2025-03
Biggest Single Number	solution	Easy	2025-03
Customers Who Bought All Products	solution	Medium	2025-03
The Number of Employees Which Report to Each Employee	solution	Easy	2025-03
Primary Department for Each Employee	solution	Easy	2025-03
Triangle Judgement	solution	Easy	2025-03
Consecutive Numbers	not solved	Medium	2025-03
Product Price at a Given Date	solution	Medium	2025-03
Last Person to Fit in the Bus	solution	Medium	2025-03
Count Salary Categories	not solved	Medium	2025-03
Employees Whose Manager Left the Company	solution	Easy	2025-03
Exchange Seats	not solved	Medium	2025-03
Movie Rating	solution	Medium	2025-03
Restaurant Growth	not solved	Medium	2025-03
Friend Requests II Who Has the Most Friends	solution	Medium	2025-03
Investments in 2016	not solved	Medium	2025-03
Department Top Three Salaries	not solved	Hard	2025-03
Fix Names in a Table	not solved	Easy	2025-03
Patients With a Condition	not solved	Easy	2025-03
Delete Duplicate Emails	not solved	Easy	2025-03
Second Highest Salary	not solved	Medium	2025-03
Group Sold Products By The Date	not solved	Easy	2025-03
List the Products Ordered in a Period	not solved	Easy	2025-03
Find Users With Valid E-Mails	not solved	Easy	2025-03