Ahf. Laender et al., AN ANALYSIS OF SQL INTEGRITY CONSTRAINTS FROM AN ENTITY-RELATIONSHIP MODEL PERSPECTIVE, Information systems, 19(4), 1994, pp. 331-358
Citations number
23
Categorie Soggetti
System Science","Information Science & Library Science","Computer Science Information Systems
This paper presents an analysis of the integrity constraints defined i
n the SQL ISO standard disclosure in the light of the entity-relations
hip model. It points out what features of integrity constraints in SQL
support which features of the entity-relationship model by discussing
how to map an entity-relationship schema into a SQL schema. In order
to organize the analysis, the paper distinguishes three levels of the
entity-relationship model. The first level corresponds to the basic mo
del, augmented with simple specializations. The second level considers
totality and more complex specializations, and allows deferred and im
mediate propagation of deletions. Finally, the third level introduces
generalization hierarchies and considers some types of inter-relations
hip constraints. For the first and second levels, the analysis indicat
es that the more complex features of the SQL referential integrity con
struct are necessary only when optimization is considered, but one of
the features - propagation of nulls - should be slightly enhanced to e
asy the optimization task. However, for the third level, the analysis
shows that, in most cases, the SQL referential integrity construct can
efficiently model subsetting, but that the direct use of SQL integrit
y constraints to account for mutual exclusion may be very expensive.