Hybrid technique for joining tables
US5241648A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 13, 1990 |
| Grant date | Aug 31, 1993 |
| Priority date | — |
| Expiry date | Feb 13, 2010 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S707/99937
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
Results of a relational data base management system are joined in a process requiring, first, existence of an index on the join columns of the inner table, and, second, ordering on the join column of the first table. First, the index on the inner table's join column is scanned for rows of the inner table having join column values matching such values of rows in the outer table. This is done in a single pass through the outer table. Next, a temporary work table containing the identifiers of inner table rows having join column values matching those of the outer table is produced by concatenating the row identifiers to their matching outer table rows. Following this, the temporary work table is ordered by the identifiers. Last, the identifier list of inner table rows is used to retrieve the corresponding rows of the inner table. All predicates local to the inner table are applied to the retrieved rows, and those satisfying these local predicates are combined with their matching outer table rows and returned to the user.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.