[Solved] Consider the table employees with columns departmen... What will the following query return?SELECT employee_id, salary, SUM(salary) OVER (PARTITION BY department) AS total_dept_salary FROM employees; | PostgreSQL

PostgreSQL - Window Functions in PostgreSQL

Consider the table employees with columns department and salary. What will the following query return?

SELECT employee_id, salary, SUM(salary) OVER (PARTITION BY department) AS total_dept_salary FROM employees;

AThe total salary of all employees in the table repeated on every row

BThe total salary for each department repeated on every employee row within that department

CThe cumulative salary ordered by employee_id within each department

DThe average salary per department for each employee

Step-by-Step Solution

Solution:

Step 1: Understand the window function
The query uses SUM(salary) OVER (PARTITION BY department), which calculates the sum of salaries grouped by department but does not collapse rows.
Step 2: Effect on rows
Each row will show the employee's salary and the total salary of their department repeated for all employees in that department.
Final Answer:
The total salary for each department repeated on every employee row within that department -> Option B
Quick Check:
Partition sums repeat per group [OK]

Quick Trick: SUM() OVER PARTITION repeats totals per group [OK]

Common Mistakes:

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Consider the table employees with columns department and salary. What will the following query return?