The Art of SQL by Stephane Faroult & Peter Robson

Author:Stephane Faroult & Peter Robson [Stephane Faroult]
Language: eng
Format: epub
Tags: COMPUTERS / Programming Languages / SQL
ISBN: 9780596555368
Publisher: O'Reilly Media
Published: 2008-12-16T16:00:00+00:00

Using OLAP functions

With databases, OLAP functions such as row_number( ) that we have already used in the self-joins situation can provide a satisfactory and sometimes even a more efficient way to answer the same question "what was the current value for one particular item at a given date?" (remember that OLAP functionality does, however, introduce a distinctly non-relational aspect to the proceedings[*]).

Note

OLAP functions belong to the non-relational layer of SQL. They represent the final, or almost final, step in query execution, since they have to operate on the post-retrieval result set after the filtering has completed.

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