Efficient optimization of a class of relational expressions
ACM Transactions on Database Systems (TODS)
The notions of consistency and predicate locks in a database system
Communications of the ACM
Optimal implementation of conjunctive queries in relational data bases
STOC '77 Proceedings of the ninth annual ACM symposium on Theory of computing
On conjunctive queries containing inequalities
Journal of the ACM (JACM)
An approach to detecting relevant updates to cached data using XML and active databases
Proceedings of the 12th International Conference on Extending Database Technology: Advances in Database Technology
| Hi-index | 0.00 |
We obtain certain results concerning the power of expressions in relational (calculus and algebra) database sublanguages. Our main results state the undecidability of the equivalence and finite equivalence problems for relational expressions. We also observe that the type of join used in a relational algebra affects the complexity of problems for that algebra. For example, using equi-joins instead of natural joins leads to unnecessarily complex expressions. We relate these results to the problems of query optimization and concurrency control.