SQL5 Done

Game_Play_Analysis I.txt

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+select player_id,min(event_date) as first_login from activity group by player_id;

Report_Contiguos_Dates.txt

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+WITH CTE AS (
+    SELECT 'failed' as period_state, fail_date as dat, rank() over(order by fail_date) as rnk from failed where year(fail_date) = 2019
+    union all
+    SELECT 'succeeded' as period_state, success_date as dat, rank() over(order by success_date) as rnk from succeeded  where year(success_date) = 2019
+) select period_state, min(dat) as start_date, max(dat) as end_date from (select *, rank() over(order by dat)-rnk as grp_rnk from cte) a group by grp_rnk,period_state order by start_date;

Students_Reported_By_Geography.txt

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+select America, Asia, Europe from(
+(SELECT @am := 1 , @as := 1, @eu := 1)t1,
+(SELEcT @as := @as + 1 as asrnk, name as 'Asia' from Student where continent = 'Asia' order by name)t2 right join
+(SELECT @am := @am + 1 as amrnk, name as 'America' from Student where continent = 'America' order by name)t3 on t2.asrnk = t3.amrnk left join
+(SELECT @eu := @eu + 1 as eurnk, name as 'Europe' from Student where continent = 'Europe' order by name)t4 on t3.amrnk = t4.eurnk)