Oracle 12c - Create materialized view results in ORA-00942
Use the CREATE MATERIALIZED VIEW statement to create a materialized view. A materialized view is a database object that contains the results of a query. The FROM clause of the query can name tables, views, and other materialized views.
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You cannot create Materialized View from Synonym. I don't know why would you like to that but we create materialized view as your working example.