公开(公告)号：CA2306928C

公开(公告)日：2004-05-25

申请号：CA2306928

申请日：2000-04-28

Applicant: IBM CANADA

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

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：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.