Useful for locating rows having a specific value in the index.
Can be hash-ordered or value-ordered.
Value-ordered NUSIs are particularly useful for enhancing the performance of range
Any access is an all-AMPs operation with the exception of the case where a NUSI is
defined on the same column set as the primary index for the table.
If an index is defined with an ORDER BY clause, it counts as 2 consecutive indexes
against the table limit of 32 secondary, hash, and join indexes (see “Importance of Consecutive Indexes for Value‑Ordered NUSIs” on page 485).
For more information about secondary indexes., see SQL Data Definition Language under the topics CREATE INDEX and CREATE TABLE.