公开(公告)号：CA2306928A1

公开(公告)日：2001-10-28

申请号：CA2306928

申请日：2000-04-28

Applicant: IBM CANADA

Inventor： HAAS PETER J ,  ZUZARTE CALISTO P ,  LUMBY JOHN E

IPC: G06F17/30

Abstract: The estimate of the selectivity of a HAVING clause in an SQL query is carrie d out by within a specified time constraint by determining a selectivity estimate for each member in a sample set of group sizes for the HAVING clause using a probabilistic model based on an assumed value distribution. The selectivity estimates for the groups in the sample set are used to interpolate estimates for all possible group sizes and the estimates are combined based on an assumed known group size distribution to provide an estimation of the selectivity for the HAVING clause. Different selectivity estimating approaches are used for each group size based on available time for estimating and on the estimated time to complete the estimate using different technique s.

公开(公告)号：CA2310576A1

公开(公告)日：2001-01-30

申请号：CA2310576

申请日：2000-06-02

Applicant: IBM

Inventor： TRUONG TUONG CHANH ,  SIDLE RICHARD S ,  LIGHTSTONE SAM S ,  COCHRANE ROBERTA JO ,  WINER MICHAEL J ,  ZUZARTE CALISTO P ,  CHAN PETRUS KAI C C ,  PIRAHESH MIR HAMID

IPC: G06F17/30

Abstract: The invention provides method and apparatus for use in a database management system for managing a database containing data, where the database has storage for storing data in the database, and has an instruction processor for processing instructions for managing da ta stored in the database. The database has a constraint manager for managing constraints on said data stored in the database. The invention provides efficient method and means for deferred checking of data after bulk loading into said database for violation of constraints by determining an appropriat e procedure for constraint checking by determining whether constraint checking is required; and if it i s required, determining whether to implement full, or incremental checking for compliance with said constraints; and then checking the data in the database in accordance with the determined constrai nt checking procedure.