Method and system for limiting the cardinality of an SQL query r

Details Method and system for limiting the cardinality of an SQL query r Method and system for limiting the cardinality of an SQL query r

1997-05-09

1999-09-21

Ho, Ruay Lian

Data processing: database and file management or data structures

Database design

Data structure types

G06F 1730

Patent

active

059567066

ABSTRACT:
A STOP AFTER clause for a relational database management system (RDBMS) structured query language (SQL) causes the RDBMS, in response to a query, to return a query result having at most a predetermined cardinality specified in the query. A query with a STOP AFTER clause is processed by the RDBMS by provision of one or more STOP operators that are inserted into a query execution plan generated by the RDBMS to execute the query. In a conservative policy, STOP operators are inserted in the query execution plan such that no tuples that might be required in the query result are discarded. In contrast, an aggressive policy inserts a STOP operator in the query execution plan wherever it is able to provide a beneficial cardinality reduction. A RESTART operator is inserted into aggressive policy query execution plans to ensure that at least the predetermined number of tuples are returned in the query result, and a final STOP operator is added at or near the root of the plan to ensure that at most the specified number of tuples are produced.

REFERENCES:
patent: 4769772 (1988-09-01), Dwyer
patent: 5367675 (1994-11-01), Chen et al.
patent: 5412804 (1995-05-01), Krishna
patent: 5412806 (1995-05-01), Du et al.
patent: 5530939 (1996-06-01), Mansfiled, Jr. et al.
patent: 5546570 (1996-08-01), McPherson, Jr. et al.
patent: 5548754 (1996-08-01), Pirahesh et al.
patent: 5548758 (1996-08-01), Pirahesh et al.
patent: 5598559 (1997-01-01), Chaudhuri
patent: 5794228 (1998-08-01), French et al.
patent: 5794229 (1998-08-01), French et al.

Affiliated with

Also associated with

Rating

Method and system for limiting the cardinality of an SQL query r does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Method and system for limiting the cardinality of an SQL query r, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and system for limiting the cardinality of an SQL query r will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-91649