anchor.diff:    
   columnClauses:
       opColumnClause+
  -    | renameColumnClause
  +    | renameColumn
       | modifyCollectionRetrieval+
       | modifyLobStorageClause+
       | alterVarrayColProperties+
       ;
   
   opColumnClause:
  -    addColumnClause
  -    | modifyColumnClauses
  +    addColumn
  +    | modifyColumn
       | dropColumnClause
       ;
       
  -addColumnClause:
  +addColumn:
       ADD
       columnOrVirtualDefinitions 
       columnProperties?
  
positive.code:      ;
   
  constraintPrimaryOrUnique:
        (PRIMARY KEY)
       | (UNIQUE columnList)
       ;
          
  
negative.code:     CHECKPOINT NUMBER
      ;
      
  renameColumn:
      RENAME COLUMN columnName TO columnName
      ;
      
  modifyCollectionRetrieval:
  