Oracle Error Message
QSM-02138: agg(expr) requires correspondng agg(expr*expr) function
Reason for the Error
The capability in question is not supported when the materialized view uses certain aggregate functions but omits an invocation of that same aggregate function on the square of the same argument.
Solution
Add an invocation of the same aggregate function on the square of the same argument (that is, the argument multiplied by itself).