Optimization of Nested Queries in a Complex Object Model (1994)
| Venue: | In Proc. of the Int. Conf. on Extending Database Technology (EDBT |
| Citations: | 15 - 2 self |
BibTeX
@INPROCEEDINGS{Steenhagen94optimizationof,
author = {Hennie J. Steenhagen and Peter M. G. Apers and Henk M. Blanken},
title = {Optimization of Nested Queries in a Complex Object Model},
booktitle = {In Proc. of the Int. Conf. on Extending Database Technology (EDBT},
year = {1994},
pages = {337--350},
publisher = {Springer-Verlag}
}
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Abstract
. Transformation of nested SQL queries into join queries is advantageous because a nested SQL query can be looked upon as a nested-loop join, which is just one of the several join implementations that may be available in a relational DBMS. In join queries, dangling (unmatched) operand tuples are lost, which causes a problem in transforming nested queries having the aggregate function COUNT between query blocks--a problem that has become well-known as the COUNT bug. In the relational context, the outerjoin has been employed to solve the COUNT bug. In complex object models supporting an SQL-like query language, transformation of nested queries into join queries is an important optimization issue as well. The COUNT bug turns out to be a special case of a general problem being revealed in a complex object model. To solve the more general problem, we introduce the nest join operator, which is a generalization of the outerjoin for complex objects. 1 Introduction Currently, at the University...
