anchor.diff:  // according the SQL reference this should not be possible
   // according to he reality it is. Here we probably apply pivot/unpivot onto whole join clause
   // eventhough it is not enclosed in parenthesis. See pivot examples 09,10,11
  +
   table_ref
       : table_ref_aux join_clause* (pivot_clause | unpivot_clause)?
       ;
  
positive.code:     : (ORDER | CLUSTER) expression BY '(' column_name (',' column_name)* ')'
      ;
  
  // $<Package DDLs
  
  drop_package
      : DROP PACKAGE BODY? (schema_object_name '.')? package_name ';'
  
negative.code:     | WAIT expression
      ;
  
  update_statement
      : UPDATE general_table_ref update_set_clause where_clause? static_returning_clause? error_logging_clause?
      ;
  
  // Update Specific Clauses
  
  update_set_clause
      : SET
        (column_based_update_set_clause (',' column_based_update_set_clause)* | VALUE '(' identifier ')' '=' expression)
  