SQL - Advanced Window Functions
Which window frame clause would you use to calculate a moving average over the current row and the two previous rows?
Which window frame clause would you use to calculate a moving average over the current row and the two previous rows?
easy📝 Conceptual Q2 of 15
Step-by-Step Solution
Solution:
Step 1: Identify the correct frame for two previous rows plus current
The frame should start 2 rows before and end at the current row.Step 2: Match with the options
ROWS BETWEEN 2 PRECEDING AND CURRENT ROW matches this:ROWS BETWEEN 2 PRECEDING AND CURRENT ROW.Final Answer:
ROWS BETWEEN 2 PRECEDING AND CURRENT ROW -> Option BQuick Check:
Two previous + current row = 2 PRECEDING to CURRENT [OK]
Quick Trick: Preceding means rows before current, following means after [OK]
Common Mistakes:
- Confusing preceding with following
- Using unbounded which includes all previous rows
- Selecting a frame that excludes current row
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