What will happen if no TOP() is specified in a USQL query with GROUP BY?

When you execute a USQL query that includes a GROUP BY clause without specifying a TOP() function, the behavior is such that the query will return results grouped according to the specified columns but not limit the number of rows returned within those groups. The results are presented based on the grouping criteria alone, spreading the data evenly across the specified columns. This means that, while you may end up with all possible groups represented in the output, the results aren't constrained to any specific maximum count per group unless explicitly limited with a TOP() function.

The outcome of the query will depend on the data set and how it is grouped rather than setting an arbitrary limit. Consequently, users may see multiple groups and varying counts within those groups based on the underlying data, which reflects a more comprehensive view of the results without the risk of truncation that specifying a TOP() might introduce.