G. von Bultingsloewen. Translating and optimizing SQL queries having aggregates. In Proc. Int. Conf. on Very Large Databases, pages 235--243, Brighton, September 1987. Morgan Kaufmann, Los Altos, Ca.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....3 Multiset (bag) has been proposed as an additional type constructor in order to formally deal with duplicates in relations. Since relational DBMSs typically do not guarantee the set property (duplicate elimination) of tables, a correct formalization has to use the concept of a multiset [34, 32, 128, 61]. Also, if SQL s aggregate operations shall be formalized, multisets are necessary. Alternatively, or in addition, one can introduce lists to cope with ordering (for example in order to express the physical storage sequence of tuples, to formalize the ORDER BY clause of SQL, or as a conceptual ....

G. von Bultingsloewen. Translating and optimizing SQL queries having aggregates. In Proc. Int. Conf. on Very Large Databases, pages 235--243, Brighton, September 1987. Morgan Kaufmann, Los Altos, Ca.

....stated, without proof, that the necessary condition for such technique is that the group by columns must be a primary key of the outer table in the join. This is the only work we know of which attempts to reduce the cost of group by by utilizing information about primary keys. Several researchers ([5, 4, 3, 10, 9]) have investigated when a nested query can be transformed into a semantically equivalent query that does not contain nesting. As part of this work, techniques to handle aggregate functions in the nested query were discussed. However, none considered interchanging the order of joins and group by. ....

Gunter von Bultzingsloewen. Translating and optimizing SQL queries having aggregates. In Proceedings of the 13th International Conference on Very Large Data Bases, pages 235--243, Brighton, England, August 1987. IEEE Computer Society Press.

....the semantics of query languages. What one does is to restrict the extended Entity Relationship model to the concepts used in the respective model. The easiest way to define semantics is to translate the query language into the calculus, as has been done for the relational query language SQL by [vB87] This way seems to us to be more flexible than the proposals of [TL85] for SQL) and [SM86, Sub87] for other data models, especially the Entity Relationship model) which map the query language directly into a theory of sets and functions. Our calculus is in particular highly suited to formally ....

....the semantics of relational query languages. Whereas relational languages like SQL or QUEL provide features for data operations and aggregate functions, the calculi do not. Klug [Klu82] was the first to suggest an extended relational calculus including at least aggregate functions, whereupon [vB87] showed us how to map SQL into a variant of this calculus. Another calculus was recently proposed in [RS90] However, it is strictly hierarchical and therefore not orthogonal. We make use of [Klu82] but we make a strict distinction between sets and bags, while he only uses sets and has to ....

[Article contains additional citation context not shown here]

G. von B ultzingsloewen. Translating and Optimizing SQL Queries Having Aggregates. In: Proc. 13th Int. Conf. on Very Large Data Bases (VLDB), P.M. Stocker, W. Kent (Eds.), VLDB Endowment Press, Saratoga (CA), pp. 235--243, 1987.

....because the existence of a primary key in each output tuple PNO in the example means that duplicates cannot exist. However, traditional dependency theory ignores three valued logic; only recently have researchers adequately documented the formal semantics of three valued logic within sql [5, 18, 22]. Because the iso standard permits Null values in any attributes of a candidate key, Null values may exist on both the left and right hand sides of a key dependency in both base and derived tables. Essentially, the problem is to determine the result of the comparison Null = Null. In sql2, the ....

....execution strategy, under certain conditions, with a variety of database architectures. Much of the earlier work in semantic transformations ignored sql s three valued logic and the presence of Null values. To help better understand these problems, Negri et al. 18] and von Bultzingsloewen [22] defined formal semantics for sql using an extended relational calculus, although neither paper tackled the problems of duplicates. A significant contribution of Negri et al. is the notion of query equivalence classes for syntactically different, yet semantically equivalent, sql queries. Several ....

Gunter von Bultzingsloewen. Translating and optimizing sql queries having aggregates. In Proc. vldb 13, pages 235--243, Brighton, England, 1987.

Online articles have much greater impact   More about CiteSeer.IST   Add search form to your site   Submit documents   Feedback  

CiteSeer.IST - Copyright Penn State and NEC