DA0-002 Data Acquisition and Preparation Practice Question
A dataset contains a column 'birthdate' in 'YYYY-MM-DD' format. The analyst needs to calculate the average age of customers as of today. Which combination of functions is most appropriate?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
DATEDIFF(year, birthdate, GETDATE())
DATEDIFF(year, birthdate, GETDATE()) returns the number of year boundaries crossed between the two dates, which is the standard SQL method for calculating age. The other options subtract year components, which gives only an estimate that ignores the month and day, leading to inaccuracies.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
AVG(YEAR(GETDATE()) - YEAR(birthdate))
Why it's wrong here
AVG aggregates, but the expression inside is not a proper age calculation.
- ✓
DATEDIFF(year, birthdate, GETDATE())
Why this is correct
DATEDIFF with year returns the number of year boundaries crossed, which is a common approximation of age.
- ✗
YEAR(GETDATE()) - YEAR(birthdate)
Why it's wrong here
This does not account for whether the birthday has occurred this year.
- ✗
EXTRACT(YEAR FROM GETDATE()) - EXTRACT(YEAR FROM birthdate)
Why it's wrong here
Same issue as A; doesn't account for month/day.
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