On Mon, 2002-08-12 at 15:00, Greg Copeland wrote: ... > Look a little deeper here. In other OO implementations, I can define a > class (say class a) which has no instances (abstract base class). > Furthermore, I can take this case and use it for building blocks > (assuming multiple inheritance is allowed in this world) by combining > with other classes (z inherits from a, b, c; whereby classes a, b, c > still do not have an actual instance). I can create an instance of my > newly inherited class (z). > > Seems to me that there is some distinction between types (classes) and > and type instances (instance of a specific class) as it pertains to it's > usability. > > How exactly would you create an abstract base class for table type?
CREATE TABLE abstract_base ( cols ..., CONSTRAINT "No data allowed in table abstract_base!" CHECK (1 = 0) ) This assumes that the constraint is not inherited or can be removed in child tables. -- Oliver Elphick [EMAIL PROTECTED] Isle of Wight, UK http://www.lfix.co.uk/oliver GPG: 1024D/3E1D0C1C: CA12 09E0 E8D5 8870 5839 932A 614D 4C34 3E1D 0C1C ======================================== "And he spake a parable unto them to this end, that men ought always to pray, and not to faint." Luke 18:1 ---------------------------(end of broadcast)--------------------------- TIP 3: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly
