How can you combine COUNT() as a window function with a filter to count only rows where status = 'active' per department?

hard📝 Application Q9 of 15

PostgreSQL - Window Functions in PostgreSQL

ACOUNT(*) FILTER (WHERE status = 'active') OVER (PARTITION BY department)

BCOUNT(status = 'active') OVER (PARTITION BY department)

CCOUNT(*) OVER (PARTITION BY department WHERE status = 'active')

DCOUNT(*) OVER (FILTER WHERE status = 'active' PARTITION BY department)

Step-by-Step Solution

Solution:

Step 1: Use FILTER clause inside COUNT()
PostgreSQL supports FILTER (WHERE condition) inside aggregate and window functions to count conditionally.
Step 2: Combine FILTER with window PARTITION BY
COUNT(*) FILTER (WHERE status = 'active') OVER (PARTITION BY department) correctly applies FILTER inside COUNT() and partitions by department.
Final Answer:
COUNT(*) FILTER (WHERE status = 'active') OVER (PARTITION BY department) -> Option A
Quick Check:
FILTER clause works inside window functions [OK]

Quick Trick: Use FILTER (WHERE ...) inside COUNT() for conditional counts [OK]

Common Mistakes:

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