This Leetcode problem Game Play Analysis III LeetCode Solution is done in SQL.

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Game Play Analysis III LeetCode Solution

Problem Statement

(player_id, event_date) is the primary key of this table. This table shows the activity of players of some game.

Each row is a record of a player who logged in and played a number of games (possibly 0) before logging out on some day using some device.

Write an SQL query that reports for each player and date, how many games played so far by the player. That is, the total number of games played by the player until that date. Check the example for clarity.

The query result format is in the following example:

Example 1:
Input:

Output:

Explanation:
For the player with id 1, 5 + 6 = 11 games played by 2016-05-02, and 5 + 6 + 1 = 12 games played by 2017-06-25.
For the player with id 3, 0 + 5 = 5 games played by 2018-07-03.
Note that for each player we only care about the days when the player logged in.

Game Play Analysis III LeetCode Solution MySQL

select 
  player_id, 
  event_date, 
  games_played_so_far 
from 
  (
    select 
      player_id, 
      event_date, 
      @games := if(
        player_id = @player, @games + games_played, 
        games_played
      ) as games_played_so_far, 
      @player := player_id 
    from 
      (
        select 
          * 
        from 
          Activity 
        order by 
          player_id, 
          event_date
      ) as a, 
      (
        select 
          @player := -1, 
          @games := 0
      ) as tmp
  ) as t;Code language: SQL (Structured Query Language) (sql)