table t : { Id : int, Nam : string, Parent : option int } PRIMARY KEY Id, CONSTRAINT Nam UNIQUE Nam, CONSTRAINT Id CHECK Id >= 0, CONSTRAINT Parent FOREIGN KEY Parent REFERENCES t(Id) fun main () = list <- queryX (SELECT * FROM t) (fn r => <xml><tr> <td>{[r.T.Id]}</td> <td>{[r.T.Nam]}</td> <td>{case r.T.Parent of None => <xml>NULL</xml> | Some id => <xml>{[id]}</xml>}</td> </tr></xml>); return <xml><body> <table> <tr> <th>Id</th> <th>Name</th> <th>Parent</th> </tr> {list} </table> <form> <table> <tr> <th>Id:</th> <td><textbox{#Id}/></td> </tr> <tr> <th>Name:</th> <td><textbox{#Nam}/></td> </tr> <tr> <th>Parent:</th> <td><textbox{#Parent}/></td> </tr> <tr> <th/> <td><submit action={add}/></td> </tr> </table> </form> </body></xml> and add r = dml (INSERT INTO t (Id, Nam, Parent) VALUES ({[readError r.Id]}, {[r.Nam]}, {[case r.Parent of "" => None | s => Some (readError s)]})); main ()