Using Outer Joins to Define Join Indexes - Teradata Database

Teradata Database Design

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Using Outer Joins to Define Join Indexes

There are several benefits in defining non-aggregate join indexes with outer joins:

  • Unmatched rows are preserved.
  • These rows allow the join index to satisfy queries with fewer join conditions than those used to generate the index.

  • Outer table row scans can provide the same performance benefits as a single-table join index.
  • For example, the Optimizer can choose to scan the outer table rows of a join index to satisfy a query that only references the outer table provided that a join index scan would be more high-performing than scanning the base table or redistributing rows.