Which DAX function is useful for creating a hierarchy from a parent-child relationship?

The PATH function is specifically designed to handle parent-child hierarchies in DAX. It takes two arguments: the column that contains the identifier for each node and the column that contains the identifier for its parent. This function returns a delimited text string that represents the unique path from a specified node to the root of the hierarchy, making it particularly useful for reporting and analysis of hierarchical data structures.

When working with parent-child relationships, utilizing the PATH function allows analysts to easily traverse and evaluate complex relationships, thus enabling better insights into the data. It provides a straightforward way to represent the chain of relationships from child to parent, which can then be leveraged in creating reports, visualizations, and further calculations.

In contrast, the other functions listed do not serve the same purpose as PATH. PATHELEMENT and PATHITEM are related but are used to extract specific components from a string created by the PATH function and do not directly create the hierarchy itself. HIERARCHY is not a valid DAX function and does not exist in the context of DAX capabilities for handling such relationships.