Jerzy Tyszkiewicz:
Spreadsheet As a Relational Database Engine,
in Proc. ACM SIGMOD International Conference on Management of Data:195-206, Indianapolis, 2010.
"Microsoft SQL Server supports connections to other OLE DB data sources on a persistent or an ad hoc basis. The persistent connection is known as a linked server; an ad hoc connection that is made for the sake of a single query is known as a distributed query.
Microsoft Excel workbooks are one type of OLE DB data source that you can query through SQL Server in this manner. This article describes the syntax that is necessary to configure an Excel data source as a linked server, as well as the syntax that is necessary to use a distributed query that queries an Excel data source."
[the first is theoretical computer science and not even intended to be practical; the second is ugly, but, at times, highly practical]
http://www.mimuw.edu.pl/~jty/SIGMOD/SIGMOD.html
And of course, http://support.microsoft.com/kb/306397:
"Microsoft SQL Server supports connections to other OLE DB data sources on a persistent or an ad hoc basis. The persistent connection is known as a linked server; an ad hoc connection that is made for the sake of a single query is known as a distributed query.
Microsoft Excel workbooks are one type of OLE DB data source that you can query through SQL Server in this manner. This article describes the syntax that is necessary to configure an Excel data source as a linked server, as well as the syntax that is necessary to use a distributed query that queries an Excel data source."
[the first is theoretical computer science and not even intended to be practical; the second is ugly, but, at times, highly practical]