A DataFrame contains product reviews with columns review_id, product_id, and reviewer_id. Some reviewers submitted the same review multiple times, creating duplicate rows with the same review_id. The team wants to remove duplicates while keeping the first occurrence. Which code should they use?

df.groupBy('review_id').count()

df.dropDuplicates(['review_id'])

df.dropDuplicates(['reviewer_id'])

A streaming pipeline produces a DataFrame of sensor readings with columns sensor_id, reading_time, and value. Due to network retries, some readings are duplicated with the same sensor_id and reading_time but different values. The team needs to keep the latest value for each sensor_id and reading_time combination. Which code should they use?

df.orderBy(col('reading_time').desc()).dropDuplicates(['sensor_id', 'reading_time'])

df.dropDuplicates(['sensor_id', 'reading_time']).select('sensor_id', 'reading_time', 'value')

df.orderBy('reading_time').dropDuplicates(['sensor_id', 'reading_time'])

df.orderBy('value').dropDuplicates(['sensor_id', 'reading_time'])

DatabricksCertified Data Engineer Associate

Domain 3Objective 4

Perform Data Deduplication Operations and Aggregate Operations on DataFrames, Such as Count, Approximate Count Distinct, and Mean, Summary. DATA-ENGINEER-ASSOCIATE Practice Questions (Page 2)

Part of the Data Transformation and Modeling domain, which accounts for 22% of the DATA-ENGINEER-ASSOCIATE exam. Databricks does not publish an official question count, but from its 90-minute exam (~35–60 total, ~8–13 in this domain), expect 1–2 from this objective — we provide 10 practice questions to prepare you well beyond it. (estimate)

10questions here

2free pages

5concepts

22%of the exam

Questions 6–10

6foundation · medium
Which function would you use to estimate the number of distinct user IDs in a large DataFrame when an exact count is not required?
Select an answer first
7foundation · medium
Which summary statistic is included in summary() but NOT in describe()?
Select an answer first
8application · medium
A DataFrame contains product reviews with columns review_id, product_id, and reviewer_id. Some reviewers submitted the same review multiple times, creating duplicate rows with the same review_id. The team wants to remove duplicates while keeping the first occurrence. Which code should they use?
Select an answer first
9foundation · medium
Which method generates summary statistics including count, mean, stddev, min, and quartiles for numeric columns?
Select an answer first
10expert · hard
A streaming pipeline produces a DataFrame of sensor readings with columns sensor_id, reading_time, and value. Due to network retries, some readings are duplicated with the same sensor_id and reading_time but different values. The team needs to keep the latest value for each sensor_id and reading_time combination. Which code should they use?
Select an answer first

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Perform Data Deduplication Operations and Aggregate Operations on DataFrames, Such as Count, Approximate Count Distinct, and Mean, Summary. DATA-ENGINEER-ASSOCIATE Practice Questions (Page 2)

Questions 6–10

Which function would you use to estimate the number of distinct user IDs in a large DataFrame when an exact count is not required?

Which summary statistic is included in summary() but NOT in describe()?

A DataFrame contains product reviews with columns review_id, product_id, and reviewer_id. Some reviewers submitted the same review multiple times, creating duplicate rows with the same review_id. The team wants to remove duplicates while keeping the first occurrence. Which code should they use?

Which method generates summary statistics including count, mean, stddev, min, and quartiles for numeric columns?

Keep studying — Data Transformation and Modeling