anchor.diff:  NULLIF: 'NULLIF';
   NULLS: 'NULLS';
   OBJECT: 'OBJECT';
  +OF: 'OF';
   OFFSET: 'OFFSET';
   OMIT: 'OMIT';
  -OF: 'OF';
   ON: 'ON';
   ONE: 'ONE';
   ONLY: 'ONLY';
  
positive.code:     : ABSENT | ADD | ADMIN | AFTER | ALL | ANALYZE | ANY | ARRAY | ASC | AT | AUTHORIZATION
      | BERNOULLI | BOTH
      | CALL | CASCADE | CATALOGS | COLUMN | COLUMNS | COMMENT | COMMIT | COMMITTED | CONDITIONAL | COPARTITION | COUNT | CURRENT
      | DATA | DATE | DAY | DEFAULT | DEFINE | DEFINER | DESC | DESCRIPTOR | DISTRIBUTED | DOUBLE
      | EMPTY | ENCODING | ERROR | EXCLUDING | EXPLAIN
      | FETCH | FILTER | FINAL | FIRST | FOLLOWING | FORMAT | FUNCTIONS
      | GRANT | DENY | GRANTED | GRANTS | GRAPHVIZ | GROUPS
      | HOUR
      | IF | IGNORE | INCLUDING | INITIAL | INPUT | INTERVAL | INVOKER | IO | ISOLATION
      | JSON
  
negative.code: DAY: 'DAY';
  DEALLOCATE: 'DEALLOCATE';
  DEFAULT: 'DEFAULT';
  DEFINE: 'DEFINE';
  DEFINER: 'DEFINER';
  DELETE: 'DELETE';
  DENY: 'DENY';
  DESC: 'DESC';
  DESCRIBE: 'DESCRIBE';
  DESCRIPTOR: 'DESCRIPTOR';
  DISTINCT: 'DISTINCT';
  DISTRIBUTED: 'DISTRIBUTED';
  DOUBLE: 'DOUBLE';
  