SQL 5 PR

AvgSalOfDeptVsCom.sql

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+SELECT departmentSalary.pay_month, department_id, 
+CASE 
+    WHEN departmentAvg > companyAvg THEN 'higher'
+    WHEN departmentAvg < companyAvg THEN 'lower'
+    ELSE 'same'
+END AS 'comparison'
+FROM (
+    SELECT date_format(pay_date, '%Y-%m') AS 'pay_month', department_id, AVG(amount) AS 'departmentAvg'
+    FROM Salary JOIN Employee ON Salary.employee_id = Employee.employee_id
+    GROUP BY department_id, pay_month
+) AS departmentSalary 
+JOIN (
+    SELECT date_format(pay_date, '%Y-%m') AS 'pay_month', AVG(amount) AS 'companyAvg'
+    FROM Salary 
+    GROUP BY pay_month
+) AS companySalary 
+ON departmentSalary.pay_month = companySalary.pay_month;

GamePlayAnalysis1.sql

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+SELECT DISTINCT player_id, MIN(event_date) OVER(PARTITION BY player_id ORDER BY event_date) AS 'first_login' 
+FROM activity;

ReportContiguousDates.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 'group_rnk' FROM CTE
+) AS y 
+GROUP BY group_rnk, period_state 
+ORDER BY start_date;

StudentsReportByGeography.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;