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