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SQL competition: the shortest interval coalesce/pack query

From: Mikito Harakiri <mikharakiri_at_iahu.com>
Date: Thu, 2 Dec 2004 17:28:40 -0800
Message-ID: <2uPrd.61$G45.36@news.oracle.com>


Write the shortest sql query that would return a minimal cover of a set of intervals. For example, given

Intervals = {(x=1,y=3), (x=2,y=5), (x=4, y=11), (x=10,y=12), (x=20,y=21)}

it should return

cover(Intervals) = {(x=1,y=12), (x=20,y=21)}

"Developing Time-Oriented..." book by R.Snordgrass demonstrates several rather lenthy solutions (pp.160+). The book is freely downloadable.

To be able to compare results, lets agree that each of the clauses (select, from, where, group by, having) starts a new line. (Each subquery/inner view must obey this rule as well.) Also, no more than 2 column expressions are allowed to fit on a single line in the select clause. Likewise, no more than 2 view/tables are allowed on a single line within from clause, no more than 2 predicates in the each line of the where clause, etc. If anybody knows alternative (maybe even standard) sql formatting rules, you are welcome to suggest those. Received on Thu Dec 02 2004 - 19:28:40 CST

Original text of this message

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