[GitHub] [trafodion] DaveBirdsall opened a new pull request #1828: [TRAFODION-3296] Fix handling of [first n] + ORDER BY subqueries

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DaveBirdsall opened a new pull request #1828: [TRAFODION-3296] Fix handling of [first n] + ORDER BY subqueries
URL: https://github.com/apache/trafodion/pull/1828
 
 
   Queries containing IN-subqueries involving both [first n] and ORDER BY were giving wrong results. The ORDER BY essentially was being ignored. This has now been fixed. The [first n] is now evaluated with respect to the ORDER BY clause.
   
   For [any n] + ORDER BY (or equivalently, LIMIT n + ORDER BY), the ORDER BY continues to be ignored, since [any n] does not specify which rows should be returned and therefore ordering has no importance.
   
   The combination [last n] + ORDER BY in an IN-subquery is now forbidden, and results in a 4484 error. The reason is that [last n] is typically used as a performance tool when used at the top level of a query, but that purpose makes no sense in the context of a subquery.

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