anchor.diff:      (FILESTREAM_ON (ignoredIdentifier_ | schemaName | STRING_))?
       ;
   
  -
   createIndexSpecification_
       : UNIQUE? (CLUSTERED | NONCLUSTERED)?
       ;
   
  -
  +alterClause_
  +    : alterColumn | addColumnSpecification | alterDrop | alterCheckConstraint | alterTrigger | alterSwitch | alterSet | alterTableTableOption | REBUILD
  +    ;
   
   
   
  
positive.code:     : PERIOD FOR SYSTEM_TIME LP_ columnName COMMA_ columnName RP_
      ;
  
  alterTableOp
      : ALTER TABLE tableName
      ;
  
  alterColumn
      : modifyColumnSpecification
      ;
  
  modifyColumnSpecification
      : alterColumnOp dataType (COLLATE collationName)? (NULL | NOT NULL)? SPARSE?
      ;
  
  alterColumnOp
      : ALTER COLUMN columnName
      ;
  
  
negative.code:     ;
  
  alterTable
      : ALTER TABLE tableName alterClause_
      ;
  
  alterIndex
  