Data Aggregation and Joins ASSOCIATE-DEVELOPER-APACHE-SPARK Practice Questions (Page 5)

Questions 21–25

1. 21foundation · easy

   In Spark 2.0 and later, what is the recommended way to concatenate DataFrames without deduplication?

   • Aunion with distinct=true
   • BunionAll
   • Cconcat
   • Dunion with distinct=false
   Reveal Solution Discussion Select an answer first
2. 22foundation · easy

   Which join type returns only rows that have matching keys in both DataFrames?

   • AFull outer join
   • BLeft join
   • CRight join
   • DInner join
   Reveal Solution Discussion Select an answer first
4. 23foundation · easy

   What does the summary() method return when called on a DataFrame?

   • AA DataFrame with rows for each statistic and columns for each numeric column
   • BA single row with all statistics concatenated
   • CA map of column names to statistics
   • DA list of statistics as strings
   Reveal Solution Discussion Select an answer first
5. 24foundation · easy

   Which DataFrame method combines two DataFrames with the same schema and removes duplicate rows?

   • Aunion
   • Bmerge
   • CunionAll
   • Dconcat
   Reveal Solution Discussion Select an answer first
6. 25application · medium

   A data analyst needs to quickly estimate the number of unique users in a very large `user_activity` DataFrame. The exact count is not critical, but the estimate should be reasonably accurate. Which method should they use?

   • AUse `approx_count_distinct` on the `user_id` column
   • BUse `count` on the `user_id` column
   • CUse `countDistinct` on the `user_id` column
   • DUse `summary` on the `user_id` column
   Reveal Solution Discussion Select an answer first