anchor.diff:     |
      ;
      //TOD NULLS_LA was used
  -   
  +
   opt_nulls_order
      : NULLS_P FIRST_P
      | NULLS_P LAST_P
  
positive.code:    ;
  
  event_trigger_value_list
     : sconst
     | event_trigger_value_list COMMA sconst
     ;
  
  altereventtrigstmt
  
negative.code:    | sql_expression
     ;
     //https://www.postgresql.org/docs/current/plpgsql-errors-and-messages.html
  
     //RAISE [ level ] 'format' [, expression [, ... ]] [ USING option = expression [, ... ] ];
  
     //RAISE [ level ] condition_name [ USING option = expression [, ... ] ];
  
     //RAISE [ level ] SQLSTATE 'sqlstate' [ USING option = expression [, ... ] ];
  
     //RAISE [ level ] USING option = expression [, ... ];
  
     //RAISE ;
  
  stmt_raise
     : RAISE opt_stmt_raise_level sconst opt_raise_list opt_raise_using SEMI
     | RAISE opt_stmt_raise_level identifier opt_raise_using SEMI
  