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Archives of the TeradataForum
Message Posted: Tue, 07 Aug 2012 @ 19:07:40 GMT
| Subj: | | Re: Concept of Index Only Scans in Teradata? |
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| From: | | Dieter Noeth |
Nathan_S_Smith wrote:
| | Some DBMSs will recognize when a query can be resolved by retrieving data only by scanning a secondary index without having to retrieve
data from the base table. | |
| | Does Teradata apply a similar concept? | |
Of course, you'll see it in Explain: ... by way of index #n without accesing the base table ...
| | With a PI on ColA and a NUSI on ColC,ColD, if a query selected only ColC and ColD would the query do a single AMP query against the
index or would it still use the base table? | |
It will use the index but NUSI access is All-AMPs not single AMP.
Dieter
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