You want to calculate a moving average of sales amounts over the last 3 days including the current day, using sales(date, amount). Which window frame clause correctly achieves this?

hard📝 Application Q8 of 15

PostgreSQL - Window Functions in PostgreSQL

You want to calculate a moving average of sales amounts over the last 3 days including the current day, using sales(date, amount). Which window frame clause correctly achieves this?

ARANGE BETWEEN INTERVAL '3 days' PRECEDING AND CURRENT ROW

BROWS BETWEEN 3 PRECEDING AND CURRENT ROW

CRANGE BETWEEN 3 PRECEDING AND CURRENT ROW

DROWS BETWEEN INTERVAL '3 days' PRECEDING AND CURRENT ROW

Step-by-Step Solution

Solution:

Step 1: Understand requirement
We want to include all rows within 3 days before current date.
Step 2: Choose correct frame type
RANGE with INTERVAL '3 days' PRECEDING includes all rows with dates in that range.
Step 3: Validate options
RANGE BETWEEN INTERVAL '3 days' PRECEDING AND CURRENT ROW uses RANGE with INTERVAL correctly; ROWS counts rows, not days.
Final Answer:
RANGE BETWEEN INTERVAL '3 days' PRECEDING AND CURRENT ROW -> Option A
Quick Check:
Use RANGE with INTERVAL for date ranges [OK]

Quick Trick: Use RANGE with INTERVAL for date-based frames [OK]

Common Mistakes:

Using ROWS for date ranges
Using numeric offsets with RANGE
Mixing INTERVAL with ROWS

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You want to calculate a moving average of sales amounts over the last 3 days including the current day, using sales(date, amount). Which window frame clause correctly achieves this?

Step 1: Understand requirement

Step 2: Choose correct frame type

Step 3: Validate options

Final Answer:

Quick Check:

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