update

Author: kamyu104

LICENSE.md

@@ -1,6 +1,6 @@
 The MIT License (MIT)
 
-Copyright (c) 2018 https://github.com/kamyu104/LeetCode-Solution
+Copyright (c) 2018 https://github.com/kamyu104/LeetCode-Solutions
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

MySQL/average-salary-departments-vs-company.sql

@@ -0,0 +1,24 @@
+# Time:  O(nlogn)
+# Space: O(n)
+
+SELECT department_salary.pay_month, department_id,
+CASE
+  WHEN department_avg < company_avg THEN 'lower'
+  WHEN department_avg > company_avg THEN 'higher'
+  ELSE 'same'
+END AS comparison
+FROM
+(
+  SELECT department_id, AVG(amount) AS department_avg, date_format(pay_date, '%Y-%m') AS pay_month
+  FROM salary JOIN employee ON salary.employee_id = employee.employee_id
+  GROUP BY department_id, pay_month
+) AS department_salary
+JOIN
+(
+  SELECT AVG(amount) AS company_avg,  date_format(pay_date, '%Y-%m') AS pay_month
+  FROM salary
+  GROUP BY date_format(pay_date, '%Y-%m')
+) AS company_salary
+ON department_salary.pay_month = company_salary.pay_month
+;
+