Ur/Web: demo/refFun.ur annotate

Subqueries may always return NULL

author	Adam Chlipala <adam@chlipala.net>
date	Thu, 03 Feb 2011 21:04:12 -0500
parents	1a317a707d71
children

rev	line source
adamc@419	1 functor Make(M : sig
adamc@419	2 type data
adamc@419	3 val inj : sql_injectable data
adamc@419	4 end) = struct
adamc@419	5
adamc@419	6 type ref = int
adamc@419	7
adamc@419	8 sequence s
adamc@419	9 table t : { Id : int, Data : M.data }
adamc@708	10 PRIMARY KEY Id
adamc@419	11
adamc@419	12 fun new d =
adamc@419	13 id <- nextval s;
adamc@471	14 dml (INSERT INTO t (Id, Data) VALUES ({[id]}, {[d]}));
adamc@419	15 return id
adamc@419	16
adamc@419	17 fun read r =
adamc@471	18 o <- oneOrNoRows (SELECT t.Data FROM t WHERE t.Id = {[r]});
adamc@501	19 case o of
adamc@419	20 None => error <xml>You already deleted that ref!</xml>
adamc@501	21 \| Some r => return r.T.Data
adamc@419	22
adamc@419	23 fun write r d =
adamc@471	24 dml (UPDATE t SET Data = {[d]} WHERE Id = {[r]})
adamc@419	25
adamc@419	26 fun delete r =
adamc@471	27 dml (DELETE FROM t WHERE Id = {[r]})
adamc@420	28
adamc@419	29 end

Mercurial > urweb