anchor.diff:  K_WHERE : W H E R E;
   K_WITH : W I T H;
   K_WITHOUT : W I T H O U T;
  -K_FIRST_VALUE : [Ff][Ii][Rr][Ss][Tt][_][Vv][Aa][Ll][Uu][Ee];
  +K_FIRST_VALUE : F I R S T'_'V A L U E;
   K_OVER  : O V E R;
   K_PARTITION : P A R T I T I O N;
   K_RANGE     : R A N G E;
  
positive.code:  |
   ;
  frameclauseOptional
   :  (K_RANGE|K_ROWS)  frame_start  
   |  (K_RANGE|K_ROWS)  K_BETWEEN  frame_start K_AND frame_end
   ;
  frame_start
   : signed_number K_PRECEDING 
  
negative.code: K_UBOUNDED   : U N B O U N D E D;
  K_CURRENT   : C U R R E N T;
  K_FOLLOWING : F O L L O W I N G;
  K_CUMEDIST  : C U M E'_'D I S T;
  K_DENSERANK : D E N S E'_'R A N K;
  K_LAG       : L A G;
  K_LASTVALUE : L A S T'_'V A L U E;
  K_LEAD       : L E A D;
  K_NTHVALUE  : N T H'_'V A L U E;
  K_NTILE      : N T I L E;
  K_PERCENTRANK : P E R C E N T'_'R A N K; 
  K_RANK       : R A N K;  
  K_ROWNUMBER  : R O W'_'N U M B E R;
  
  
  IDENTIFIER
  