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Message Posted: Fri, 30 Apr 2004 @ 13:33:21 GMT
| Subj: || || Re: Information on COVER INDEX and query optimization... |
| From: || || Ramakrishna_Vedantam |
Just check the Teradata design manual to understand covering. To quote the manual 'The Optimizer aggressively pursues NUSIs when they cover a
query. The expression "covering" means that all of the columns requested in a query are also available from an existing index subtable, making it
unnecessary to access the base table rows to complete the query.' There are some simple examples too.