Data Engineering Associate with Databricks Practice Exam

Which function can be used to remove duplicate elements from an array in SQL?

1. Flatten

2. Collect_set

3. Explode

4. Current_timestamp

The correct answer is: Collect_set

The function that effectively removes duplicate elements from an array in SQL is the collect_set function. This function aggregates input values into an array while automatically eliminating duplicates. Essentially, when you apply collect_set to a set of values, it collects all unique elements into an array format, making it a valuable tool for ensuring that only distinct data points are retained. In contrast, other options do not serve the purpose of removing duplicates. For instance, flatten is used to transform a nested array structure into a flat array but does not perform any deduplication. Explode is employed to convert an array into multiple rows, thereby creating a row for each element without eliminating duplicates. Current_timestamp retrieves the current date and time but has no relevance to arrays or deduplication processes. Collect_set is the optimal choice for this task due to its ability to provide a distinct collection of values from an input dataset.