@inproceedings{4ca044bed7a0443b9bb0ee8a0133468f,
title = "Unnesting arbitrary queries",
abstract = "SQL-99 allows for nested subqueries at nearly all places within a query. From a user's point of view, nested queries can greatly simplify the formulation of complex queries. However, nested queries that are correlated with the outer queries frequently lead to dependent joins with nested loops evaluations and thus poor performance. Existing systems therefore use a number of heuristics to unnest these queries, i.e.. de-correlate them. These unnesting techniques can greatly speed up query processing, but are usually limited to certain classes of queries. To the best of our knowledge no existing system can de-correlate queries in the general case. We present a generic approach for unnesting arbitrary queries. As a result, the de-correlated queries allow for much simpler and much more efficient query evaluation.",
author = "Thomas Neumann and Alfons Kemper",
year = "2015",
language = "English",
series = "Lecture Notes in Informatics (LNI), Proceedings - Series of the Gesellschaft fur Informatik (GI)",
publisher = "Gesellschaft fur Informatik (GI)",
pages = "383--402",
editor = "Kai-Uwe Sattler and Wolfram Wingerath and Harald Schoning and Steffen Friedrich and Thomas Seidl and Norbert Ritter and Theo Harder",
booktitle = "Datenbanksysteme fur Business, Technologie und Web, BTW 2015 - Proceedings",
note = "16. Fachtagung {"}Datenbanksysteme fur Business, Technologie und Web{"}, BTW 2015 - 16th Conference on Database Systems for Business, Technology and Web, BTW 2015 ; Conference date: 04-03-2015 Through 06-03-2015",
}