What does a durable key in snapshot tables allow for?

A durable key in snapshot tables is essential for maintaining data integrity and ensuring that similar entities can be accurately grouped and summarized. This key serves as a stable reference point that allows for consistent identification of records over time, despite any temporal changes in data.

When you associate a durable key with entities in a snapshot table, it ensures that rows belonging to the same entity can be easily grouped together for reporting, analysis, or data management purposes. This process is critical in scenarios where you need to derive insights or trends related to specific patient populations, treatments, or outcomes based on historical data.

While unique identification of medication orders and accurate counting of patients are important functions in data management, the primary advantage of a durable key is its role in grouping and summarizing rows for analysis. This capability is what truly enables comprehensive and meaningful insights from the dataset, making option C the most accurate choice.