Patent Number: 6,167,399

Title: Join index for relational databases

Abstract: The retrieval of data from a computerized database is optimized through the use of a join index. A denormalized base table is converted into a plurality of normalized tables and the join index for the normalized tables is created by combining one or more commonly-used columns of the normalized tables. Outer joins are used to generate the join index, instead of inner joins, so that the join index satisfies queries with fewer join conditions than the ones used to generate the join index. Each row of the join index comprises a fixed part and a repeated part. The fixed part is stored only once in each row, but the repeated part is comprised of recursive levels within each row, so that each row may contain as many repeated parts as needed. In addition, each of the repeated parts comprises a fixed part and a repeated part.

Inventors: Hoang; Chi Kim (Palo Alto, CA)

Assignee: NCR Corporation

International Classification: G06F 17/30 (20060101); G06F 017/30 ()

Expiration Date: 12/26/2017