Analytical functions are in use and a RANK has been specified.
PUSHED RANK is the analytical equivalent of a
SORT ORDER BY STOPKEY and is being used within an
OVER () call.
Analytical calls can be very useful, but as not everyone understands them, watch out for maintainability and as always - test to ensure they minimise machine load and execution time.
SELECT * FROM
( SELECT spmnt, totalamount, upmnt,
**RANK()** OVER (PARTITION BY upmnt ORDER BY totalamount DESC) "RANKING"
) WHERE **RANKING** <= 5;
- Oracle Magazine - How to read an execution plan
- Oracle Tuning Guide - Explaining and Displaying Execution Plans
- Oracle Tuning Guide - Comparing Execution Plans Tutorial
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