15.00 - Using Outer Joins to Define Simple Join Indexes - Teradata Database

Teradata Database Design

prodname
Teradata Database
vrm_release
15.00
category
User Guide
featnum
B035-1094-015K

Using Outer Joins to Define Simple Join Indexes

Because join indexes generated from inner joins do not preserve unmatched rows, you should consider using outer joins to define simple join indexes, noting the following restrictions.

  • Inequality conditions are not supported under any circumstances for ON clauses in join index definitions.
  • Outer joins are not supported under any circumstances for aggregate join indexes.
  • Defining join indexes on outer joins enables them to satisfy queries with fewer join conditions than those used to generate the index. See “Defining a Simple Join Index on a Binary Join Result” on page 542 and “Using Outer Joins to Define Join Indexes” on page 559 for a demonstration of this property.

    Also see “Restriction on Coverage by Join Indexes When a Join Index Definition References More Tables Than a Query” on page 577 and related examples.