Query processing in a system for distributed databases (SDD-1)
ACM Transactions on Database Systems (TODS)
Extending the database relational model to capture more meaning
ACM Transactions on Database Systems (TODS)
Database abstractions: aggregation and generalization
ACM Transactions on Database Systems (TODS)
Using Semi-Joins to Solve Relational Queries
Journal of the ACM (JACM)
Distributed query processing in a relational data base system
SIGMOD '78 Proceedings of the 1978 ACM SIGMOD international conference on management of data
Towards a sound view integration methodology
PODS '83 Proceedings of the 2nd ACM SIGACT-SIGMOD symposium on Principles of database systems
Processing Queries Over Generalization Hierarchies in a Multidatabase System
VLDB '83 Proceedings of the 9th International Conference on Very Large Data Bases
View Processing in MULTIBASE, A Heterogeneous Database System
ER '81 Proceedings of the Second International Conference on the Entity-Relationship Approach to Information Modeling and Analysis
Database integration and query optimization in multi-database systems
Database integration and query optimization in multi-database systems
Outerjoin optimization in multidatabase systems
DPDS '90 Proceedings of the second international symposium on Databases in parallel and distributed systems
A database management capability for Ada
WADAS '85 Proceedings of the second annual Washington Ada symposium on Ada: Ada in the mainstream: applications and education
Query Optimization in Multidatabase Systems Considering Schema Conflicts
IEEE Transactions on Knowledge and Data Engineering
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A multidatabase system provides a logically integrated view of existing, possibly inconsistent, databases. Logical integration is achieved primarily through the use of generalization, which can be modelled algebraically as a sequence of outerjoin and aggregation operations. Conventional distributed query processing techniques are inadequate for processing queries over views defined by outerjoins and aggregates. In a conventional distributed database system, selections and projections are inexpensive to process; hence joins have been the rocus of most previous research. In a multidatabase system, however, even selections and projections can be as expensive as joins. The semiouterjoin operation can potentially reduce query processing costs. In general, there may be many different strategies based on semiouterjoins for processing a given query. The query optimization problem is to choose the most profitable of these strategies. This paper studies the query optimization problem for selection and projection queries. It develops linear-time solutions to the problem, and then extends these solutions to provide heuristics for joins and conjunctive queries.