Handling null values in SQL queries over object-oriented data

Details Handling null values in SQL queries over object-oriented data Handling null values in SQL queries over object-oriented data

1997-04-04

1999-05-18

Amsbury, Wayne

Data processing: database and file management or data structures

Database design

Data structure types

707 2, 707 3, 707 4, 707 5, 707103, 707202, G06F17/30

Patent

active

059059826

ABSTRACT:
A method, apparatus, and article of manufacture for handling NULL values in SQL queries over object oriented data. A two-phase method is used to enable a query evaluator in a two-valued logic environment to properly handle occurrences of NULL values for predicates that involve subqueries, i.e., basic subquery predicates and/or quantified subquery predicates. For basic subquery predicates, negation reduction is performed by applying logical equivalence rules and inverting basic comparators (e.g., transforming < to >=) to eliminate NOTs. Then, transformations are employed for the resulting positive predicates to include NULL value testing, i.e., NULL protection. For quantified subquery predicates, in addition to performing negation reduction, quantified subqueries are converted into existential subqueries. In most cases, this yields a predicate that can be handled using NULL protection transformations for positive predicates. The exception (i.e., a "NOT EXISTS" resulting from the conversion step of a universally quantified subquery) is handled using NULL protection transformations for negative predicates. The evaluation of the NULL tested positive and negative predicates ensures that if a predicate has a NULL value, it is not included in the query result.

REFERENCES:
patent: 5504885 (1996-04-01), Alashqur
patent: 5590324 (1996-12-01), Leung et al.
patent: 5630120 (1997-05-01), Vachey
patent: 5713015 (1998-01-01), Goel et al.
patent: 5724570 (1998-03-01), Zeller et al.
patent: 5732258 (1998-03-01), Jakobsson et al.
patent: 5761493 (1998-06-01), Blakeley et al.
patent: 5774692 (1998-06-01), Boyer et al.
Subqueries in SQLF, a fuzzy database query language, Patrick Bosc, 1995 IEEE (Cat. No. 95CH3576-7) (ISBN: 0 7803 2559 1) p. 3636-41, vol. 4, 22-25 Oct. 1995.
Query execution strategies for missing data in distributed hetrogeneous object databases, Koh et al., p. 466-73, IEEE Computer Soc. Press, ISBN: 0 8186 7399 0 , 27-30 May 1996.
Won Kim, "Object-Oriented Database Systems: Promises, Reality, and Future", Proc. 19th VLDB Conference, Dublin, Ireland, Aug., 1993.
Michael J. Carey et al., "A Data Model and Query Language for EXODUS", Proc. ACM SIGMOD International Conference on Management of Data, Chicago, Illinois, Jun., 1988.
Won Kim, "A Model of Queries for Object-Oriented Databases", Proc. 15th VLDB Conference, Amsterdam, The Netherlands, Aug., 1989.
Francois Bancilhon et al., "A Query Language for the O.sub.2 Object-Oriented Database System", Proc. 2nd International Workshop on Database Programming Languages, Morgan-Kaufmann Publishers, Inc., Gleneden Beach, Oregon, Jun., 1989.
Jack Orenstein et al., "Query Processing in the ObjectStore Database System", Proc. ACM SIGMOD International Conference on Management of Data, San Diego, California, Jun., 1992.
Michael Kifer et al., "Querying Object-Oriented Databases", Proc. ACM SIGMOD International Conference on Management of Data, San Diego, California, Jun., 1992.
S. Dar et al., "CQL++: A SQL for the Ode Object-Oriented DBMS", Proc. 3rd International Conference on Extending DataBase Technology, Advances in Database Technology-EDBT '92, Springer-Verlag, Vienna, Mar. 1992.
Jose A. Blakeley et al., "Experiences Building the Open OODB Query Optimizer", Proc. ACM SIGMOD International Conference on Management of Data, Washington, D.C., May, 1993.
Charles Lamb et al., "The ObjectStore Database System", Communications of the ACM, Oct., 1991.

Affiliated with

Also associated with

Rating

Handling null values in SQL queries over object-oriented data does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Handling null values in SQL queries over object-oriented data, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Handling null values in SQL queries over object-oriented data will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-1769104