TY - GEN
T1 - Equivalence of queries combining set and bag-set semantics
AU - Cohen, Sara
PY - 2006
Y1 - 2006
N2 - The query equivalence problem has been studied extensively for set-semantics and, more recently, for bag-set semantics. However, SQL queries often combine set and bag-set semantics. For example, an SQL query that returns a multiset of elements may call a ubquery or view that returns a set of elements. As another example, in SQL one can compute a multiset-union of queries, each of which returns a set of answers. This paper presents combined semantics, which formally models query evaluation combining set and bag-set semantics. The equivalence problem for queries evaluated under combined semantics is studied. A sufficient condition for equivalence is presented. For several important common classes of queries necessary and sufficient conditions for equivalence are presented.
AB - The query equivalence problem has been studied extensively for set-semantics and, more recently, for bag-set semantics. However, SQL queries often combine set and bag-set semantics. For example, an SQL query that returns a multiset of elements may call a ubquery or view that returns a set of elements. As another example, in SQL one can compute a multiset-union of queries, each of which returns a set of answers. This paper presents combined semantics, which formally models query evaluation combining set and bag-set semantics. The equivalence problem for queries evaluated under combined semantics is studied. A sufficient condition for equivalence is presented. For several important common classes of queries necessary and sufficient conditions for equivalence are presented.
KW - Bag semantics
KW - Combined semantics
KW - Datalog
KW - Query equivalence
KW - Set semantics
UR - http://www.scopus.com/inward/record.url?scp=34250651743&partnerID=8YFLogxK
U2 - 10.1145/1142351.1142362
DO - 10.1145/1142351.1142362
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AN - SCOPUS:34250651743
SN - 1595933182
SN - 9781595933188
T3 - Proceedings of the ACM SIGACT-SIGMOD-SIGART Symposium on Principles of Database Systems
SP - 70
EP - 79
BT - Proceedings of the Twenty-Fifth ACM SIGMOD-SIGACT-SIGART Symposium on Principles of Database Systems, PODS 2006
T2 - 25th ACM SIGMOD-SIGACT-SIGART Symposium on Principles of Database Systems, PODS 2006
Y2 - 26 June 2006 through 28 June 2006
ER -