anchor.diff:      : PERIOD FOR SYSTEM_TIME LP_ columnName COMMA_ columnName RP_
       ;
   
  -alterColumn
  -    : modifyColumnSpecification
  -    ;
  -
   modifyColumnSpecification
       : alterColumnOperation dataType (COLLATE collationName)? (NULL | NOT NULL)? SPARSE?
       ;
  
positive.code:     : columnName (ASC | DESC)?
      ;
  
  columnNameGeneratedClause
      : columnNameGenerated DEFAULT simpleExpr (WITH VALUES)? COMMA_ columnNameGenerated
      ;
  
  columnNameGenerated
      : columnName dataTypeName_ GENERATED ALWAYS AS ROW (START | END)? HIDDEN_? (NOT NULL)? (CONSTRAINT ignoredIdentifier_)?
      ;
  
  
negative.code:     ;
  
  alterClause_
      : modifyColumnSpecification | addColumnSpecification | alterDrop | alterCheckConstraint | alterTrigger | alterSwitch | alterSet | alterTableTableOption | REBUILD
      ;
  
  
  