How to Fetch Maximum Row for Each Group Using SQL

sql-queries-3/sql-max-value-row-group/set_up_Schema.sql

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+CREATE TABLE Employees ( 
+	id SERIAL PRIMARY KEY, 
+	name VARCHAR(100), 
+	department VARCHAR(50), 
+	salary DECIMAL(10, 2)
+);
+
+INSERT INTO employees (name, department, salary) VALUES
+('Alice', 'HR', 60000),
+('Bob', 'HR', 80000),
+('Charlie', 'IT', 90000),
+('Dave', 'IT', 85000),
+('Eve', 'Finance', 75000),
+('Frank', 'Finance', 70000),
+('Grace', 'HR', 62000),
+('Hank', 'HR', 81000),
+('Ivy', 'IT', 92000),
+('Jack', 'IT', 86000),
+('Karen', 'Finance', 77000),
+('Leo', 'Finance', 72000),
+('Mia', 'HR', 64000),
+('Nate', 'HR', 82000),
+('Olivia', 'IT', 93000),
+('Paul', 'IT', 87000),
+('Quinn', 'Finance', 78000),
+('Rita', 'Finance', 73000),
+('Steve', 'HR', 65000),
+('Tina', 'HR', 83000),
+('Uma', 'IT', 94000),
+('Victor', 'IT', 88000),
+('Wendy', 'Finance', 79000),
+('Xander', 'Finance', 74000),
+('Yara', 'HR', 66000),
+('Zane', 'HR', 84000),
+('Amy', 'IT', 95000),
+('Brian', 'IT', 89000),
+('Cathy', 'Finance', 80000),
+('Dan', 'Finance', 76000),
+('Ella', 'HR', 67000),
+('Finn', 'HR', 85000),
+('Gina', 'IT', 96000),
+('Henry', 'IT', 90000),
+('Irene', 'Finance', 81000),
+('Jake', 'Finance', 77000),
+('Kate', 'HR', 68000),
+('Luke', 'HR', 86000),
+('Megan', 'IT', 97000),
+('Nick', 'IT', 91000),
+('Olga', 'Finance', 82000),
+('Pete', 'Finance', 78000),
+('Quincy', 'HR', 69000),
+('Rose', 'HR', 87000),
+('Sam', 'IT', 98000),
+('Tom', 'IT', 92000),
+('Ursula', 'Finance', 83000),
+('Vince', 'Finance', 79000),
+('Wade', 'HR', 70000),
+('Xena', 'HR', 88000);

sql-queries-3/sql-max-value-row-group/using_CTEs.sql

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+WITH MaxSalaries AS ( 
+	SELECT department, MAX(salary) AS max_salary 
+	FROM Employees 
+	GROUP BY department
+ ) 
+SELECT e.id, e.name, e.department, e.salary 
+FROM Employees e 
+JOIN MaxSalaries ms ON e.department = ms.department AND e.salary = ms.max_salary;

sql-queries-3/sql-max-value-row-group/using_WindowFunctions.sql

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+SELECT id, name, department, salary 
+FROM ( 
+    SELECT id, name, department, salary,
+	 ROW_NUMBER() OVER (PARTITION BY department ORDER BY salary DESC) AS rn 
+    FROM Employees 
+) sub 
+WHERE rn = 1;

sql-queries-3/sql-max-value-row-group/using_subqueries.sql

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+SELECT id, name, department, salary 
+FROM Employees e1 
+WHERE salary = ( 
+	SELECT MAX(salary) 
+	FROM Employees e2 
+	WHERE e1.department = e2.department 
+);