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Re: ?s regarding sparse indexes


And one of those sparse indexes might be a SELECT/OMIT LF, which are now considered as candidates for optimization - this is because the default in QAQQINI for IGNORE_DERIVED_INDEX is now *NO.


On 5/1/2014 2:21 PM, Nathan Andelin wrote:
Here's a quote from the Information Center:

"You can use the SQL CREATE INDEX statement to create a sparse index using
SQL selection predicates.

Last release users were given the ability to use the SQL CREATE INDEX statement
to create a sparse index using a WHERE condition. With this support, the
query optimizer recognizes and considers sparse indexes during its
optimization. If the query WHERE selection is a subset of thesparse index WHERE
selection, then the sparse index is used to implement the query. Use of the
sparse index usually results in improved performance."

So you can reference "tables" in SQL select statements, but under the
covers the query optimizer may use the sparse index.

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