What does the ROW_NUMBER() OVER (PARTITION BY department ORDER BY salary DESC) window function do in a query?

easy📝 Conceptual Q11 of 15

PostgreSQL - Window Functions in PostgreSQL

What does the ROW_NUMBER() OVER (PARTITION BY department ORDER BY salary DESC) window function do in a query?

ACounts the number of employees in each department.

BAssigns a unique rank to each employee within their department based on salary, starting at 1 for the highest salary.

CCalculates the total salary for each department.

DReturns the average salary of all employees.

Step-by-Step Solution

Solution:

Step 1: Understand ROW_NUMBER() with PARTITION BY
The function assigns a unique sequential number to rows within each department group.
Step 2: ORDER BY salary DESC ranks highest salary first
Ordering by salary descending means the highest salary gets row number 1 in each department.
Final Answer:
Assigns a unique rank to each employee within their department based on salary, starting at 1 for the highest salary. -> Option B
Quick Check:
ROW_NUMBER() with PARTITION BY and ORDER BY = ranked rows [OK]

Quick Trick: ROW_NUMBER() numbers rows per group ordered by criteria [OK]

Common Mistakes:

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