다음과 같이 해보세요.

PROCEDURE PRC_TEST IS   

  ln_count number;

BEGIN  

    SELECT count(*) INTO ln_count
      FROM user_mviews
      WHERE mview_name = 'MV_TEST';

    IF ln_count > 0 THEN    
      execute immediate
       'drop materialized view MV_TEST;

    END IF;    

    execute immediate 
    'create materialized view MV_TEST
      refresh complete on demand
      as
      select 'X' from dual';  

EXCEPTION
 WHEN OTHERS THEN
 RAISE;      
END PRC_TEST;