Databricks Certified Associate Developer for Apache Spark — Question 116

QUESTION NO: 75 -

Which of the following code blocks returns a DataFrame where column divisionDistinct is the approximate number of distinct values in column division from DataFrame storesDF?

Answer options

• A. storesDF.withColumn("divisionDistinct", approx_count_distinct(col("division")))
• B. storesDF.agg(col("division").approx_count_distinct("divisionDistinct"))
• C. storesDF.agg(approx_count_distinct(col("division")).alias("divisionDistinct"))
• D. storesDF.withColumn("divisionDistinct", col("division").approx_count_distinct())
• E. storesDF.agg(col("division").approx_count_distinct().alias("divisionDistinct"))

Correct answer: C

Explanation

The correct answer, C, uses the agg function to apply approx_count_distinct on the division column and aliases the result as divisionDistinct, thus creating a new DataFrame with the desired structure. Option A incorrectly uses withColumn instead of agg, while option B misuses the method by attempting to apply approx_count_distinct directly on the column reference. Options D and E also have incorrect usages of the methods, with D trying to use withColumn inappropriately and E having a redundant alias on the count distinct method.