SQL - Advanced Query Patterns
Which SQL clause is essential to limit the number of rows returned per group in a Top-N per group query?
Which SQL clause is essential to limit the number of rows returned per group in a Top-N per group query?
easy📝 Conceptual Q2 of 15
Step-by-Step Solution
Solution:
Step 1: Identify the clause that groups rows for numbering
ThePARTITION BYclause groups rows so functions likeROW_NUMBER()restart numbering per group.Step 2: Understand its role in limiting rows per group
UsingPARTITION BYwithROW_NUMBER()allows filtering top N rows per group.Final Answer:
PARTITION BY -> Option DQuick Check:
Limiting rows per group needs PARTITION BY [OK]
Quick Trick: Use PARTITION BY to group rows for Top-N numbering [OK]
Common Mistakes:
- Using GROUP BY alone to limit rows per group
- Confusing WHERE with PARTITION BY
- Using HAVING without aggregation
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