Databricks Data Engineer Associate Question 155
Select 2You are working with a DataFrame in Databricks containing a column named event_time with timestamp values. You need to extract the year and month from this timestamp column to perform grouping operations. Which of the following options demonstrate correct methods to achieve this in PySpark?
- A
df = df.withColumn('year', year(col('event_time'))).withColumn('month', month(col('event_time')))
- B
df = df.withColumn('year', col('event_time').year).withColumn('month', col('event_time').month)
- C
df = df.withColumn('year', extract('year', col('event_time'))).withColumn('month', extract('month', col('event_time')))
- D
df = df.withColumn('year', date_format(col('event_time'), 'y')).withColumn('month', date_format(col('event_time'), 'MM'))
- E
df = df.withColumn('year', col('event_time').substr(1, 4)).withColumn('month', col('event_time').substr(6, 2))
Show answer and explanation
Correct answers: A, D
Explanation
Extracting calendar data from a timestamp column in PySpark can be effectively done using either the year and month functions or the date_format function with appropriate format strings. These methods are optimized for working with timestamp types and ensure accuracy and clarity. Other methods, such as using attributes, unsupported functions, or substring extraction, are either invalid or not recommended in professional scenarios.
- A. Correct.
This is correct. The
yearandmonthfunctions in PySpark are explicitly designed to extract the respective calendar components from a timestamp column. - B. Incorrect.
This is incorrect. There is no direct
yearormonthattribute on the column object in PySpark; attempting to use these attributes will result in an error. - C. Incorrect.
This is incorrect. PySpark does not have an
extractfunction for this purpose. Using this will result in a syntax error. - D. Correct.
This is correct. The
date_formatfunction can extract specific parts of a timestamp column by specifying the desired format (e.g., 'y' for year, 'MM' for month). - E. Incorrect.
This is incorrect. While the
substrfunction can technically retrieve parts of a string, it is not a reliable or recommended approach for extracting calendar data from a timestamp column, as timestamps are not guaranteed to follow a fixed format.