What happens if no aggregation function is specified in a query?

When no aggregation function is specified in a query in Adobe Campaign Classic, the system does not know how to handle the data that is being requested. Consequently, this lack of guidance leads to the query being improperly formed, resulting in an error.

Aggregation functions serve a critical role, as they define how groups of data should be processed or summarized. Functions such as COUNT, SUM, AVG, MAX, and MIN are essential for providing meaningful results from the data being queried. When a query is created without specifying how to aggregate the data, the system cannot execute it correctly, and therefore, it generates an error to indicate that the query cannot be processed successfully.

The other options described would not accurately represent what happens in this situation. For example, the query does not automatically execute without an aggregation function; rather, it requires that specification. Similarly, the query does not default to a simple select operation, nor does it provide empty results—both scenarios would imply that the query was operational in some form, whereas the absence of an aggregation function directly leads to an error.