An improved join dependency for efficient constraint checking
In a relational database model, checking the contraints of join dependency involves examining a set of n tuples and solving m1 constraint equalities. We derive a scheme called the (n,m)-JD in which the number of constraint equalities is reduced to m2, by forming cyclic combinations of the (disjoint) elements of the partition and increasing the number of intersection operations to obtain the projections in the constraint equalities. The reduced set of constraint equalities results in less elementary checking operations and hence an overall increase in efficiency in the normalization effort. The relationship among (n,m)-JDs of various degrees and orders is also studied and formalised.
KeywordsDatabase design join dependency constraint checking
Unable to display preview. Download preview PDF.
- [BeVa81]Berri, C. and Vardi, M., "On the Properties of Total Join Dependencies", H. Gallaire, J. Minker, and J. M. Nicolas (Ed), Advances in Database Theory, Vol. 1, Plenum Press, New York, 1981, pp. 25–71.Google Scholar
- [Codd71]Codd, E. F., "Normalized Data Base Structure: A Brief Tutorial", Proc. 1971 ACM SIGFIDET Workshop on Data Description, Access and Control, San Diego, Ca., Nov. 11–12, 1971, E. F. Codd and A. L. Dean (Eds).Google Scholar
- [Codd72]Codd, E. F., "Further Normalization of the Data Base Relational Model", Data Base System, R. Rustin (Ed), Courant Computer Science Symposium, Vol. 6, Prentice-Hall, Englewood Cliffs, N.J., 1972, pp. 33–64.Google Scholar
- [Fagi79]Fagin, R., "Normal Forms and Relational Database Operators", Proc. 1979 ACM SIGMOD Intl. Conf. on Management of Data, Boston, Mass., May 1979. Also IBM Research Report RJ2471, Feb. 19, 1979.Google Scholar
- [Gyss85]Gyssens, M., "Embedded Join Dependencies as a tool for decomposing Full Join Dependencies", Proc. 4th ACM SIGACT-SIGMOD Symposium on Principles of Database Systems, March 1985, pp. 205–214.Google Scholar
- [Maie83]Maier, D., The Theory of Relational Databases, Computer Science Press, 1983.Google Scholar
- [Nico78]Nicolas, J. M., "Mutual Dependencies and Some Results on Undecomposable Relations", Proc. 4th Int. Conf. on Very Large Data Bases, West Berlin, Germany, Sept. 1978, pp. 360–367.Google Scholar
- [Riss78]Rissanen, J., "Theory of Joins for Relational Databases — A Tutorial Survey", Proc. 7th Sym. on Math. Foundations of Comp. Sc., Lecture Notes in Computer Sc. 64, Winkowski (ed), Spring-Verlag, New York, 1978, pp. 537–551.Google Scholar
- [Tan84]Tan, K. P., "A Less Costly Constraints Checking for Join Dependency", Proc. of the 10th Intl. Conference on Very Large Data Bases, Aug. 1984, pp. 63–68.Google Scholar
- [Ullm82]Ullman, J. D., Principles of Database Systems, Computer Science Press, Potomac, Maryland, 1982.Google Scholar