PDE Preparing and Using Data for Analysis Practice Question

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

• ✗

  Use the FORMAT_DATE function to create the `sale_month` column.

  Why it's wrong here

  FORMAT_DATE is used to format a date as a string, not to extract an integer month. While you could use FORMAT_DATE('%m', sale_date) to get a two-digit month string, the requirement is to extract the month, which typically implies an integer. EXTRACT(MONTH FROM sale_date) is the direct and correct function. FORMAT_DATE would return a string, which may not be desired and is less efficient.

• ✓

  Use the EXTRACT function in the SELECT list to create the `sale_month` column.

  Why this is correct

  To add a column that extracts the month from a date, you use the EXTRACT function: `EXTRACT(MONTH FROM sale_date) AS sale_month`. This returns an integer representing the month. You can include this expression in the SELECT list of your query, and when you create a table from the query, the new column will be included. This is the correct way to derive the month from a date column.

• ✗

  Use a LIMIT clause to restrict the number of rows to only those in 2023.

  Why it's wrong here

  LIMIT restricts the number of rows returned but does not filter based on conditions. It cannot ensure that only rows from 2023 are included; it would simply take an arbitrary number of rows. To filter by year, you need a WHERE clause with a date condition. LIMIT is used for sampling or previewing, not for conditional filtering.

• ✗

  Use a HAVING clause to filter on `region` and `sale_date`.

  Why it's wrong here

  The HAVING clause is used to filter groups after aggregation, not individual rows. Since there is no aggregation in this scenario, using HAVING would be incorrect. It would also cause an error if used without GROUP BY. The WHERE clause is the correct place to filter rows before any grouping. This is a common mistake for those familiar with SQL but not the specific semantics of HAVING.

• ✓

  Use a WHERE clause with conditions on `region` and `sale_date`.

  Why this is correct

  To filter rows, you use a WHERE clause. For the region condition, you can write `region = 'North America'`. For the date condition, you can use `EXTRACT(YEAR FROM sale_date) = 2023` or a range like `sale_date BETWEEN '2023-01-01' AND '2023-12-31'`. This is the standard way to restrict rows in a query. Combining both conditions with AND ensures only rows meeting both criteria are included.