Data Engineering Associate with Databricks Practice Exam

What does the flatten function do in SQL?

1. Converts rows into columns

2. Combines multiple arrays into a single array

3. Removes duplicates from an array

4. Restructures data into a flat schema

The correct answer is: Combines multiple arrays into a single array

The flatten function in SQL is primarily used to combine multiple arrays into a single array. This function is particularly useful in scenarios where you are dealing with nested data structures, such as arrays of arrays, and you want to simplify that structure by consolidating the elements into one array. Utilizing the flatten function allows data engineers to streamline complex datasets, making them easier to query and analyze. When you flatten an array, it reduces the complexity of working with nested structures and enables straightforward operations and functions to be applied to the data. In this context, while other options touch on relevant operations, only combining multiple arrays into a single array accurately defines the specific behavior of the flatten function. For instance, converting rows into columns typically pertains to pivot operations, removing duplicates is related to the distinct functions, and restructuring data into a flat schema aligns more with the concepts of normalization or data modeling rather than the specific functionality of flattening arrays.