On Sat, 3 Sep 2005, Robert D. Kennedy wrote: > I have seen in another thread that sub-queries in a CHECK > constraint have implementation ramifications that make them awkward to > implement and support. OK, fair enough, c'est la vie. > > ERROR: cannot use subquery in check constraint > > is the result. I have a model which seems to BEG for just such a feature > though. What alternatives are there to the use of CHECK(SELECT()) in > this model?
The simplest thing is to place the select into a function and use a check constraint on that (with appropriate row locks). However, that won't prevent removal or change of a referenced row. You can use triggers to prevent that (in your case to prevent removal or change of id of a referenced node or the change of type of a referenced mode away from directory). At that point, you might be just as well off using a trigger to do the initial check as well. ---------------------------(end of broadcast)--------------------------- TIP 5: don't forget to increase your free space map settings
