anchor.diff:      | varrayColProperties
       ;
       
  -modifyColumnClauses:
  +modifyColumn:
       MODIFY 
       ( 
           LEFT_PAREN modifyColProperties (COMMA modifyColProperties)* RIGHT_PAREN
  
positive.code:      ;
   
  constraintPrimaryOrUnique:
        (PRIMARY KEY)
       | (UNIQUE columnList)
       ;
          
  
negative.code:     ;
  
  alterExternalTable:
      ( addColumn
      | modifyColumn
      | dropColumn
      | parallelClause
      | externalDataProperties
      | (REJECT LIMIT ( NUMBER | UNLIMITED ))
  