The compute clause section of Chapter 3, “Using Aggregates, Grouping, and Sorting” should contain the following information:
A system test may fail because there are too many aggregates in the compute clause of a query. The number of aggregates that each compute clause can accommodate is limited to 127, and if a compute clause contains more than 127 aggregates, the system generates an error message when you try to execute the query.
Each avg() aggregate counts as two aggregates when you are counting toward the limit of 127, because an avg() aggregate is actually a combination of a sum() aggregate and a count() aggregate.
