Adding and renaming columns in Apache Spark - Cheat Sheet & Quick Revision

Recall & Review

beginner

How do you add a new column to a Spark DataFrame?

Use the withColumn method with the new column name and the expression or value for the column.<br>Example: df.withColumn('new_col', df['existing_col'] + 1)

beginner

What does the withColumnRenamed method do in Spark?

It renames an existing column in a DataFrame.<br>Example: df.withColumnRenamed('old_name', 'new_name') changes the column name from old_name to new_name.

intermediate

Can you chain multiple withColumn calls to add several columns?

Yes, you can chain withColumn calls to add or modify multiple columns.<br>Example: df.withColumn('col1', expr1).withColumn('col2', expr2)

intermediate

What happens if you use withColumn with a column name that already exists?

The existing column is replaced with the new values or expression provided.<br>This is useful for modifying columns.

intermediate

Is it possible to rename multiple columns at once in Spark DataFrame?

Spark does not have a built-in method to rename multiple columns at once.<br>You can chain multiple withColumnRenamed calls or use a loop to rename columns.

Which method adds a new column to a Spark DataFrame?

A drop

B withColumnRenamed

C select

D withColumn

withColumn adds or replaces a column in a Spark DataFrame.

What does withColumnRenamed('old', 'new') do?

A Renames column 'old' to 'new'

B Adds a new column named 'new'

C Deletes column 'old'

D Duplicates column 'old' as 'new'

It renames the column named 'old' to 'new'.

If you call withColumn on an existing column name, what happens?

A An error occurs

B The column is duplicated

C The existing column is replaced

D Nothing changes

The existing column is replaced with the new values or expression.

How can you rename multiple columns in Spark DataFrame?

A Use a single <code>withColumnRenamed</code> with multiple names

B Chain multiple <code>withColumnRenamed</code> calls

C Use <code>withColumn</code>

D Use <code>select</code> only

You chain multiple withColumnRenamed calls or use a loop to rename multiple columns.

Which of these is NOT a valid way to add a column in Spark?

A df.withColumnRenamed('old_col', 'new_col')

B df.withColumn('new_col', df['existing_col'] + 1)

C df.withColumn('new_col', lit(5))

D df.select('*', (df['existing_col'] * 2).alias('new_col'))

withColumnRenamed renames columns; it does not add new columns.

Explain how to add a new column and rename an existing column in a Spark DataFrame.

Think about methods that modify DataFrame columns.

Describe what happens when you use withColumn on a column that already exists.

Consider if the column is duplicated or replaced.