Incorporating Hypothetical Views and Extended Recursion into SQL Database Systems
نویسندگان
چکیده
Current database systems supporting recursive SQL impose restrictions on queries such as linearity, and do not implement mutual recursion. In a previous work we presented the language and prototype R-SQL to overcome those drawbacks. Now we introduce a formalization and an implementation of the database system HR-SQL that, in addition to extended recursion, incorporates hypothetical reasoning in a novel way which cannot be found in any other SQL system, allowing both positive and negative assumptions. The formalization extends the fixpoint semantics of R-SQL. The implementation improves the efficiency of the previous prototype and is integrated in a commercial DBMS.
منابع مشابه
Soft stratification for transformation-based approaches to deductive databases
The efficient evaluation of recursive views is a crucial issue in the research field of deductive databases. Results in this area are especially relevant for systems which will implement the new SQL:1999 standard, and hence will allow the definition of stratifiable recursive views. In particular, transformation-based solutions to query evaluation seem to be well-suited for extending existing re...
متن کاملMaintaining Views Incrementally Extended Abstract
We present incremental evaluation algorithms to compute changes to materialized views in relational and deductive database systems, in response to changes (insertions, deletions, and updates) to the relations. The view deenitions can be in SQL or Datalog, and may use UNION, negation, aggregation (e.g. SUM, MIN), linear recursion, and general recursion. We rst present a counting algorithm that t...
متن کاملData Retrieval and Aggregates in SQL*/NR
Standard SQL is incapable of handling recursive database queries and nested relations. A proposed solution to allow recursion in SQL was given in SQL KC93], while a solution to allow nested relations in SQL was given in SQL=NF RKB87]. However, these two problems with SQL were handled separately, and an extended SQL that handles both recursive queries and nested relations is still lacking. To ov...
متن کاملAn Amateur's Introduction to Integrity Constraints and Integrity Checking in SQL
In this paper we survey the various forms of integrity constraints provided in SQL. A critical discussion of the implications of SQL's approach to integrity follows, particularly identifying misconceptions to be found in some textbooks. The relationship between views and constraints in SQL is investigated and contrasted with the state-ofthe-art in integrity checking for deductive databases. As ...
متن کاملFormalizing a Broader Recursion Coverage in SQL
SQL is the de facto standard language for relational databases and has evolved by introducing new resources and expressive capabilities, such as recursive definitions in queries and views. Recursion was included in the SQL-99 standard, but this approach is limited as only linear recursion is allowed, mutual recursion is not supported, and negation cannot be combined with recursion. In this work...
متن کامل