anchor.diff:      CHECKPOINT NUMBER
       ;
       
  -renameColumnClause:
  -    RENAME COLUMN columnName TO 
  +renameColumn:
  +    RENAME COLUMN columnName TO columnName
       ;
       
   modifyCollectionRetrieval:
  
positive.code:      ;
   
  constraintPrimaryOrUnique:
        (PRIMARY KEY)
       | (UNIQUE columnList)
       ;
          
  
negative.code:     ;
  
  columnOrVirtualDefinitions:
      LEFT_PAREN 
          columnOrVirtualDefinition
          (COMMA columnOrVirtualDefinition)* 
      RIGHT_PAREN
      |columnOrVirtualDefinition
      ;
      
  columnOrVirtualDefinition:
  