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Practice › LeetCode › LeetCode (archived) › LeetCode 01xx ›

LeetCode 175: Combine Two Tables

Problem Restatement We are given two tables: Person and Address . The Person table stores each person's ID, first name, and last name. The Address table stores address records. Each address belongs to a person through personId . We need to report this information for every person: firstName, lastName, city, state The important part is that every person must appear in the result, even if that person has no address....

Practice › LeetCode › LeetCode (archived) › LeetCode 05xx ›

LeetCode 550: Game Play Analysis IV

Problem Restatement We are given a table named Activity . Each row records one player's login activity on one date. We need to report the fraction of players who logged in again on the day immediately after their first login date. The final answer must be rounded to 2 decimal places. The result has one column: fraction The task is to count players with day-two retention, then divide by the...

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LeetCode 574: Winning Candidate

Problem Restatement We are given two tables. Candidate : Column Type Meaning id int Candidate id name varchar Candidate name Vote : Column Type Meaning id int Vote id candidateId int The candidate who received this vote We need to report the name of the candidate who received the largest number of votes. The test cases guarantee exactly one winner. The result table can be returned in any order because...

Practice › LeetCode › LeetCode (archived) › LeetCode 05xx ›

LeetCode 512: Game Play Analysis II

Problem Restatement We are given an Activity table. Each row records one player login on one date, including the device used and the number of games played. We need to report the device that each player used on their first login date. The result can be returned in any order. The table has columns player_id , device_id , event_date , and games_played ; (player_id, event_date) is the primary key. The...

Practice › LeetCode › LeetCode (archived) › LeetCode 02xx ›

LeetCode 262: Trips and Users

Problem Restatement We are given two tables: Trips and Users . Trips stores taxi trip requests. Users stores user information, including whether a user is banned. We need to find the cancellation rate for each day from: '2013-10-01' to: '2013-10-03' Only trips where both the client and driver are unbanned should be counted. The cancellation rate is: cancelled requests / total requests Cancelled means the trip status is either: 'cancelled_by_driver'...

Practice › LeetCode › LeetCode (archived) › LeetCode 01xx ›

LeetCode 184: Department Highest Salary

Problem Restatement We are given two tables: Employee and Department . Employee stores employee information. Column Type id int name varchar salary int departmentId int Department stores department information. Column Type id int name varchar Each employee belongs to one department through Employee.departmentId . We need to find employees who have the highest salary in each department. If multiple employees share the highest salary in the same department, we return...

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LeetCode 175: Combine Two Tables

LeetCode 550: Game Play Analysis IV

LeetCode 574: Winning Candidate

LeetCode 512: Game Play Analysis II

LeetCode 262: Trips and Users

LeetCode 184: Department Highest Salary