anchor.diff:      | delete_statement
       | insert_statement
       | lock_table_statement
  +    | merge_statement
       | rollback_statement
       | savepoint_statement
       | select_statement
  
positive.code: 
  lock_table_statement :
          LOCK TABLE swallow_to_semi
      ;
  
  rollback_statement :
  
negative.code: LIKE : 'like' ;
  LIMIT : 'limit' ;
  LOCK	:	'lock';
  MERGE : 'merge' ;
  NOT : 'not' ;
  NOTFOUND:	'notfound';
  NULL : 'null' ;
  