SQL5 Submitted

Problem1.sql

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+WITH CTE AS(
+SELECT fail_date as 'dat' , 'failed' As period_state , rank() OVER(ORDER by fail_date) as 'rnk' from failed
+ WHERE YEAR(fail_date) = 2019
+UNION ALL
+SELECT success_date  as 'dat' , 'succeeded' As period_state, 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 diff from CTE)as y
+group by diff, period_state
+order by start_date;

Problem2.sql

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+WITH first as(
+    SELECT name as 'America', ROW_NUMBER() OVER(ORDER BY name) AS 'rnk' From student WHERE continent = 'America'
+),
+second as(
+    SELECT name as 'Asia', ROW_NUMBER() OVER(ORDER BY name) AS 'rnk' From student WHERE continent = 'Asia'
+),
+third as(
+    SELECT name as 'Europe', ROW_NUMBER() OVER(ORDER BY name) AS 'rnk' From student WHERE continent = 'Europe'
+)
+
+SELECT America , Asia , Europe FROM second RIGHT JOIN first on first.rnk = second.rnk LEFT JOIN third 
+ON first.rnk = third.rnk;

Problem3.sql

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+WITH companyAvg as(
+    Select date_format(pay_date,'%Y-%m') as 'pay_month',
+    AVG(amount) as 'companyavg' from salary group by pay_month
+),
+deptAvg as(
+    Select date_format(pay_date,'%Y-%m') as 'pay_month',
+    department_id, AVG(amount) as 'deptavg' from salary join employee
+    ON salary.employee_id = employee.employee_id
+    group by department_id, pay_month
+)
+SELECT deptAvg.pay_month, department_id,
+(
+    CASE
+        WHEN deptavg>companyavg THEN 'higher'
+        WHEN deptavg<companyavg THEN 'lower'
+        ELSE 'same'
+    END
+) as 'comparison' from companyAvg JOIN deptAvg ON
+deptAvg.pay_month = companyAvg.pay_month

Problem4.sql

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+WITH CTE AS(SELECT player_id, event_date as 'first_login', RANK() OVER (PARTITION BY player_id order by event_date) as 'rnk' from activity)
+Select player_id, first_login from CTE where rnk = 1