Path: utzoo!dptcdc!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!cs.utexas.edu!uunet!cimshop!dsm
From: dsm@cimshop.UUCP (David Masterson)
Newsgroups: comp.databases
Subject: Re: Nesting SQL Commands?
Message-ID: <421@cimshop.UUCP>
Date: 18 Apr 89 16:28:11 GMT
References: <4YGLTiy00VA-MCvmVY@andrew.cmu.edu>
Organization: Consilium Mt. View CA
Lines: 16
In-reply-to: dp22+@andrew.cmu.edu's message of 17 Apr 89 05:36:46 GMT

In message <4YGLTiy00VA-MCvmVY@andrew.cmu.edu>, dp22+@andrew.cmu.edu writes:
>     Is there an implementation of SQL around that will allow functions
>to be nested in the same where clause?
>i.e.
>
>   WHERE    AVG(Col1 + Col2) = MIN(AVG(Col1+Col2))
>
What is the MINimum of an AVeraGe?  An average is only one number just like
a minimum is.  An aggregate function takes as input a set of numbers and 
produces a number as output.  Therefore, nesting two aggregate functions
like above doesn't make sense, but does the following?

	WHERE MIN(col1) > MIN(col2 + AVG(col1))

David Masterson
uunet!cimshop!dsm		or		DMasterson@cup.portal.com