Oracle Error QSM-02176: MV with UNION ALL in a view is too complex

Oracle Error Message

QSM-02176: MV with UNION ALL in a view is too complex

Reason for the Error

If a materialized view has a view whose definition involves a UNION ALL query, then the materialized view’s defining query cannot have any clauses other than SELECT or FROM. Other clauses such as WHERE, HAVING, CONNECT BY, or GROUP BY are not allowed. Further more, the FROM clause should have only one item.

Solution

Remove any clauses besides SELECT and FROM from the materialized view’s defining query.