DECLARE
   str     VARCHAR2 (1000);
   l_cnt   NUMBER;
BEGIN
   FOR cur_t IN (SELECT table_name
                   FROM user_tables)
   LOOP
      BEGIN
         str :=
               'SELECT COUNT(*) FROM '
            || cur_t.table_name
            || ' WHERE pogon = ''400501'''; 

         -- In the WHERE clause above I knew which column I'm 
         -- searching for - it was 'pogon'. You'd use 
         -- USER_TAB_COLUMNS.COLUMN_NAME instead
			
         EXECUTE IMMEDIATE (str)
                      INTO l_cnt;

         IF l_cnt > 0
         THEN
            DBMS_OUTPUT.put_line (cur_t.table_name);
         END IF;
      EXCEPTION
         WHEN OTHERS
         THEN
            NULL;
      END;
   END LOOP;
END;
/