SQL - Advanced Window Functions
What is the purpose of using a window frame clause like
ROWS BETWEEN 1 PRECEDING AND CURRENT ROW in a moving average calculation?What is the purpose of using a window frame clause like ROWS BETWEEN 1 PRECEDING AND CURRENT ROW in a moving average calculation?
easy📝 Conceptual Q1 of 15
Step-by-Step Solution
Solution:
Step 1: Understand the window frame clause
The clauseROWS BETWEEN 1 PRECEDING AND CURRENT ROWmeans the window includes the current row and the one immediately before it.Step 2: Apply to moving average calculation
Calculating average over this window means averaging the current row's value and the previous row's value.Final Answer:
To calculate the average including the current row and the one before it -> Option AQuick Check:
Window frame clause = Current + 1 preceding row [OK]
Quick Trick: Window frames define which rows to include in calculations [OK]
Common Mistakes:
- Thinking it averages all rows in the table
- Ignoring the 'preceding' keyword
- Assuming it excludes the current row
Master "Advanced Window Functions" in SQL
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