Data Engineering Associate with Databricks Practice Exam

What is the primary function of the collect_set function in SQL?

1. To aggregate and summarize data

2. To collect unique values from a column

3. To filter datasets based on conditions

4. To limit the size of result sets

The correct answer is: To collect unique values from a column

The function collect_set in SQL is primarily used to collect unique values from a specified column within a dataset. When you apply this function to a column, it essentially groups the values and eliminates any duplicates, returning a set of distinct entries. This is particularly useful when you want to understand the unique items present in a dataset without worrying about redundancy. For instance, if you have a dataset with repeated entries for certain categorical data, using collect_set will give you a list of only the unique entries, making it easier to analyze the diversity within that data. The options related to aggregating data or summarizing information may involve different functions designed for those purposes, such as sum, avg, or count, which perform calculations rather than merely collecting unique items. Similarly, filtering datasets based on specific conditions typically utilizes functions like WHERE, and limiting the size of result sets is conducted through clauses such as LIMIT, neither of which aligns with the primary function of collect_set.