Ochen\' interesno.. Ne uveren chto budet ochen\' polezno..
Nu nachnem s togo chto tebe dlia takih veshei kak UNION statement nado kak minimum MySQL4. Ili Oracle. Nashet generetsii nomerov s pomoshiu cartesian product - eto printsip peremnozhenia matrits. Dumaiu ne ochen\' slozhnyi algoritm !
Nashet takih veshei kak generatsii nomerov s pomoshiu SQL, ia dumaiu ty eto luchshe na liubom imperative iazyke programmirovania napishesh\', chem na deklarativnom. Ia dumaiu eto ravnosil\'no pisat\' guestbook s bazoi dannyh v LISP ili Prolog !
Hotia hochu tebe skazat\' takim SQL statementam kak UNION, DIFF, PRODUCT, INTERSECTION uchat v liubom kurse po Oracle! Ottuda i matematichskie dokazatel\'sta naprimer togo chto INTERSECTION statement mozhno iz UNION i DIFF napisat\'.
No statia interesnaia...