Query languages for bags
Stéphane Grumbach, Leonid O. Libkin, Tova Milo, Limsoon Wong · ACM SIGACT News · 1996
One of the characteristics of advanced database systems is that they must handle data which no longer fits the traditional relational style.The present column summarizes recent results on one such extension, where databases handle bags (multisets) rather than just sets.The results illustrate an important research direction in Database Theory.