[Solved] How can you use NTILE to assign deciles to a dataset and then filter only the top 10% of rows? — Ans: Use NTILE(10) OVER (ORDER BY value DESC) and filter where bucket = 1 | PostgreSQL

PostgreSQL - Window Functions in PostgreSQL

How can you use NTILE to assign deciles to a dataset and then filter only the top 10% of rows?

AUse NTILE(10) OVER (ORDER BY value DESC) and filter where bucket = 1

BUse NTILE(100) OVER (ORDER BY value) and filter where bucket <= 10

CUse NTILE(10) OVER (ORDER BY value) and filter where bucket = 10

DUse NTILE(10) OVER (ORDER BY value) and filter where bucket = 1

Step-by-Step Solution

Solution:

Step 1: Assign deciles with NTILE(10)
NTILE(10) splits data into 10 groups ordered by value.
Step 2: Filter top 10%
Ordering DESC puts highest values first; bucket 1 is top 10%.
Final Answer:
Use NTILE(10) OVER (ORDER BY value DESC) and filter where bucket = 1 -> Option A
Quick Check:
Top decile = bucket 1 when ordering DESC [OK]

Quick Trick: Order DESC to get top values in bucket 1 [OK]

Common Mistakes:

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How can you use NTILE to assign deciles to a dataset and then filter only the top 10% of rows?